Perylene-based redox polyimides as cathode material for aqueous rechargeable zinc ion battery

Abstract

The present invention generally relates to cathode material (108) for aqueous rechargeable zinc ion battery. Specifically, the present invention relates to modified cathode material (108) comprising perylene-based polyimides. More particularly, the present invention relates to synthesis of organic electrode materials including PI-COF and PI-DAAQ based on carbonyl groups. Further, the present invention relates to synthesis of PI-COF and PI-DAAQ by incorporating a redox-active perelyetertacarboxylic dianhydride (PTCDA) as the connecting unit.

Description

[0001] PERYLENE-BASED REDOX POLYIMIDES AS CATHODE MATERIAL FOR AQUEOUS RECHARGEABLE ZINC ION BATTERY

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to cathode material for aqueous rechargeable zinc ion battery. Specifically, the present invention relates to modified cathode material comprising perylene -based polyimides. More particularly, the present invention relates to synthesis of organic electrode materials including PLCOF and PLDAAQ based on carbonyl groups. Further, the present invention relates to synthesis of PLCOF and PLDAAQ by incorporating a redox-active perylene tetracarboxylic dianhydride (PTCDA) as the connecting unit.

[0004] BACKGROUND OF THE INVENTION

[0005] The emerging demand for portable electrical devices and electric vehicles has driven the development of rechargeable batteries. Zinc ion batteries have emerged as promising alternatives to lithium-ion batteries due to their safety, low cost, excellent water compatibility, high volumetric capacity, and abundance. However, in aqueous rechargeable zinc-ion batteries (ARZIBs), where zinc metal is directly used as an anode and intercalative materials as cathode, the lack of suitable cathode materials with high capacity and excellent cycling stability hinders their widespread application.

[0006] Researchers worldwide face the challenge of developing suitable cathode materials with stable structures for ARZIBs. Inorganic intercalative materials, including conventional metal oxides like Mn, V, and Mo-based oxides, sulfides, polyanions, and Prussian blue analogs, have been investigated as cathodes. However, these materials suffer from issues such as irreversible capacity loss, the use of toxic and environmentally unfriendly elements, and high costs, limiting their application.

[0007] Organic redox-active materials have shown promise as alternatives to inorganic materials in batteries due to their high energy density and redox potentials. However, organic anhydride materials, despite their potential, have not received much attention due to their high solubility in organic electrolytes, low electronic conductivity, and poor stability.

[0008] To address these challenges, researchers have explored various approaches to improve the performance of organic cathode materials. One common approach is to enhance electronic conductivity by creating composites with highly conducting materials. Another strategy involves polymerization of anhydride compounds with amine groups to improve stability during redox reactions.

[0009] Polyimide materials have garnered significant interest as potential cathode materials for zinc-ion batteries. Polyimides are known for their excellent thermal stability, mechanical strength, and chemical resistance, making them suitable for battery applications. Additionally, polyimides can be chemically modified or functionalized to enhance their electrochemical performance, facilitating the reversible intercalation of zinc ions during charging and discharging processes. Moreover, polyimides can be easily processed into thin films or coatings, which are desirable for battery applications.

[0010] MR Raj et al. (Sustainable Energy & Fuels 5.1, 2021, 175-187) report the synthesis of Polyimide using PTCDA and 2,6 diamino anthraquinone in the presence of imidazole and zinc acetate which is used as cathode material in the application of lithium and sodium ion batteries. Ruby Raj, Michael, et al. (ACS Applied Energy Materials 3.1, 2019, 240-252) reports the synthesis of perylene diimide-benzidine (PDI-Bz) and perylene diimide -urea (PDI-Ur) using PTCDA with amino precursors and imidazole as the solvent and zinc acetate as a catalyst, which is used as cathode materials for lithium and sodium ion batteries. However, the use of zinc acetate and imidazole for the polymerization of polyimide may not be ideal for several reasons as they may interfere with the desired polymerization pathway leading to poor yields, incomplete reactions, or the formation of undesired byproducts. Additionally, the presence of zinc acetate and imidazole could introduce contaminants into the polyimide polymer, affecting its properties and performance. Moreover, the methods disclosed by above studies are complicated, expensive and non-scalable.

[0011] Therefore, Polymerization or cyclization is an effective approach to suppress the solubility of organic electrode materials in electrolytes and improve the cycling performances of these materials in rechargeable ZIBs (Zinc ion batteries). There is a significant need for the development of a scalable, cost-effective, and environmentally friendly synthesis approach for perylene -based redox polyimides that could be used as high-performance cathode materials for aqueous zinc-ion batteries. This type of material may exhibit enhanced cycling stability and better compatibility with aqueous electrolytes; therefore, so as to advance sustainable and efficient energy storage systems. OBJECTS OF THE INVENTION

[0012] An object of the present invention is to provide a novel cathode material including perylene-based polyimides.

[0013] Another object of the present invention is to synthesize organic electrode materials, including PI- COF and PI-DAAQ, based on carbonyl groups.

[0014] Another object of the present invention is to develop scalable and cost-effective processes for the synthesis of organic cathode materials for ARZIBs.

[0015] Another object of the present invention is to explore the use of polyimides as a class of polymers for enhancing performance of organic cathode materials in ARZIBs.

[0016] SUMMARY OF THE INVENTION

[0017] The present invention generally relates to modified cathode material cathode material (108) comprising perylene-based polyimides. More particularly, the present invention relates to synthesis of organic electrode materials including PI-COF and PI-DAAQ based on carbonyl groups. The present invention also relates to synthesis of PI-COF and PI-DAAQ by incorporating a redox-active perylenetetracarboxylic dianhydride (PTCDA) as the connecting unit.

[0018] In an aspect, the present invention relates to a cathode material for aqueous zinc-ion battery comprising perylene-based polyimide, wherein the cathode material shows X-ray Diffraction peaks at 11.7°, 25.7° and 27.6°, and is a semi-crystalline in nature; and wherein a surface area of the cathode material is in the range of 90.3 m2g-1to 182 m2g-1.

[0019] In an embodiment, the cathode material is selected from polyimide diamino anthraquinone (PI- DAAQ) material and polyimide covalent organic framework (PI-COF) material.

[0020] In an embodiment, the cathode material is resistant to dissolution in aqueous electrolyte, and is thermally stable.

[0021] In an embodiment, the cathode material comprises TT— 7r stacking of perylene structural backbone with diamino anthraquinone and / or covalent organic framework.

[0022] In an embodiment, the cathode material has FTIR peaks selected from 1690 cm-1relevant to carbonyl group (C=O), 3461 cm-1and 3409 cm-1relevant for amino group, 1600 cm-1relevant for perylene, and 1500 and 1400 cm-1relevant for triazine. In an embodiment, the cathode material comprises uniform spatial distribution of C, N, and O elements.

[0023] In an embodiment, the cathode material is mesoporous in nature.

[0024] In an embodiment, the cathode material comprises ordered TT— TT stacking and lamellar packing structures of perylene -based polyimide.

[0025] In an embodiment, the PI-COF cathode material comprises rod shaped morphology, and has 2D conjugated framework of perylene with covalent organic framework.

[0026] In an embodiment, the PI-DAAQ cathode material comprises rod shaped morphology, and has 2D linear framework of perylene with diamino anthraquinone.

[0027] In an embodiment, the cathode material comprises high-density electroactive imide functionalities for Zn2+-ion storage.

[0028] In an embodiment, the cathode material is metal-free and recyclable.

[0029] In an embodiment, the surface area of the material is in the range of 100 m2g-1to 182 m2g-1.

[0030] In an embodiment, the cathode material comprises ordered and porous framework.

[0031] In another aspect, the present invention relates to a process for preparation of the cathode material as claimed in claim 1, comprising: a) hydrolyzing perylenetetracarboxylic dianhydride (PTCDA) with water followed by adding a solvent to obtain PTCDA solution; b) dropwise adding an amine solution into the PTCDA solution of step a) under continuous stirring for a time period in the range of 1-3 hours to obtain a mixture; c) heating the mixture of step b) at temperature in the range of 200-220 °C for a time period in the range of 45-50 hours to obtain insoluble solid material; and d) washing the insoluble solid material of step c) followed by drying to obtain the cathode material.

[0032] In an embodiment, the solvent used in step a) is N-Methylpyrrolidone (NMP), dimethylformamide, N, N-dimethylacetamide, and dimethylsulfoxide or any of mixture thereof.

[0033] In an embodiment, the amine solution comprises an amine in N-Methylpyrrolidone (NMP).

[0034] In an embodiment, the amine is selected from but not limited to melamine, 2, 6-diamino anthraquinone, diamine, diaminobenzene, diaminonaphthalene, and diamino pyridine.

[0035] In an embodiment, the diaminobenzene is selected from but not limited to 1,4-diaminobenzene, and 1,3-diaminobenzene. In an embodiment, the diaminonaphthalene is selected from but not limited to 1,5- diaminonaphthalene, and 1,8-diaminonaphthalene.

[0036] In an embodiment, the washing of step d) is done using solvent selected from water, methanol, ethanol, propanol and butanol or any of mixture thereof.

[0037] In an embodiment, the drying of step d) is done in a vacuum oven at temperature in the range of 90-110 °C.

[0038] In another aspect, the present invention provides an aqueous zinc-ion battery (100) comprising said cathode material (108).

[0039] In an embodiment, the aqueous zinc-ion battery (100) additionally comprises: i) anode (104), ii) current collector, iii) aqueous electrolyte, iv) separator (106), v) positive case (114), vi) negative case (102), viii) spacer (110), and ix) spring (112).

[0040] In an embodiment, the anode is selected from zinc foil, and preintercalated zinc electrode.

[0041] In an embodiment, the current collector is selected from Gra foil, stainless steel foil and titanium foil.

[0042] In an embodiment, the aqueous electrolyte is selected from zinc sulphate (ZnSCM), zinc acetate, and zinc trifluromethanesulfonate.

[0043] In an embodiment, the separator is selected from glass fiber membrane, polypropylene separator and cellulose separator.

[0044] In an embodiment, the aqueous electrolyte is having concentration in the range of 1 to 3 M.

[0045] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.

[0046] BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Fig. 1 illustrates (a) XRD of PTCDA, PI COF, and PI DAAQ and (b) & (c) shows the FTIR spectra of PI COF, PI DAAQ and their ligands.

[0048] Fig. 2 illustrates a) FESEM and ED AX mapping of PI-COF, and b) FESEM and ED AX mapping of PI-DAAQ.

[0049] Fig. 3 illustrates dissolution properties of the PI-COF and PI-DAAQ polymer with their monomer in 2M ZnSO4 electrolyte.

[0050] Fig. 4 illustrates CV curves of a) PI-COF at 0.5 mVs”1, b) PI-DAAQ and c) PTCDA. Fig. 5 illustrates (a and b) rate capability data of PI-COF and PI-DAAQ, (c and d) GCD profiles at various current densities (the 2ndcycles of each current density) and (e and f) cycling performance at 1000 mA g1of PI-COF and PI-DAAQ, respectively.

[0051] Fig. 6 shows (a & b) BET surface area of PI COF and PI DAAQ materials, and (c & d) pore size distribution of the PI COF and PI DAAQ materials.

[0052] Fig. 7 shows cycling performance of the PI COF material up to 4000 cycles or more.

[0053] Fig. 8 shows (a) and (b) cycling performance of the PI COF and PI DAAQ materials for 200 cycles at 100 mAg1.

[0054] Fig. 9 shows the representative aqueous zinc ion battery (100) as coin cell.

[0055] DETAILED DESCRIPTION OF THE INVENTION

[0056] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[0057] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”

[0058] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise.

[0059] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be constructed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.

[0060] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it is individually recited herein.

[0061] All processes described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any nonclaimed element essential to the practice of the invention.

[0062] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0063] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.

[0064] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

[0065] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and / or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description that follows, and the embodiments described herein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.

[0066] It should also be appreciated that the present invention can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.

[0067] The term “semi-crystalline material” is used in the present specification which refers to a solid / particle(s) that contains both crystalline and amorphous regions. The crystalline regions exhibit a high degree of order, while the amorphous regions are disordered.

[0068] The present invention generally relates to modified cathode material (108) comprising perylene- based polyimides. More particularly, the present invention relates to synthesis of organic electrode materials including PI-COF and PLDAAQ based on carbonyl groups. The present invention also relates to synthesis of PI-COF and PI-DAAQ by incorporating a redox-active perylenetetracarboxylic dianhydride (PTCDA) as the connecting unit.

[0069] In an aspect, the present invention provides a modified cathode material (108) including perylene- based polyimide, wherein the polyimide is selected from PI-DAAQ and polyimide covalent organic framework (PI-COF).

[0070] In various embodiments, polyimides (Pls) can be synthesized from a variety of monomers, including dianhydrides and diamines. The choice of monomers help in determining the properties of the resulting PI.

[0071] In various embodiments, PI-DAAQ and PI-COF are resistant to dissolution in aqueous electrolytes with good thermal stability.

[0072] In another aspect, the present invention relates to a process for synthesis of modified cathode material (108) including perylene-based polyimides, including the steps of: a) hydrolyzing perylenetetracarboxylic dianhydride (PTCDA) with 2.0 equivalent of H2O followed by adding it to N-Methylpyrrolidone (NMP) solution in a beaker; b) dropwise adding melamine dispersed in NMP into the beaker with continuous stirring for a duration of 2 hours; c) heating for a duration of 48 hours at 210° C followed by washing with methanol and DI water to obtain reddish-brown color insoluble solids; d) drying in a vacuum oven at 100° C to obtain PI-COF; and e) carrying out steps a) to d) except for the precursor used is 2,6 diamino anthraquinone in place of melamine at step b) to obtain PI-DAAQ.

[0073] In various embodiments, a scheme for the process for synthesis of modified cathode material (108) including perylene-based polyimides is given as:

[0074] PI-COF

[0075] Scheme 1 : Synthesis of the PI-DAAQ and PI -COF polymer by condensation polymerization.

[0076] In various embodiments, polymerization of PTCDA is carried out using amino derivatives such as anthraquinone derivative and melamine to synthesize 2D linear and conjugate PI-DAAQ and PI- COF, respectively.

[0077] In certain embodiments, the amino derivatives may also include various amine-containing compounds such as diamines, diaminobenzenes, diaminonaphthalene, diamino pyridines, or other related compounds. The choice of the amino derivative influences the properties of the resulting polymer.

[0078] In certain embodiments, the amino derivatives includes diaminobenzene derivatives such as l,4diaminobenzene and l,3diaminobenzene; and diaminonaphthalene derivatives such as 1,5- diaminonaphthalene and 1,8-diaminonaphthalene.

[0079] In various embodiments, the polyimide synthesized using N-Methylpyrrolidone (NMP) as solvent exhibit excellent electrochemical performance and stable behavior in Zinc ion battery compared to existing polyimides. In various embodiments, PI-COF exhibit specific capacity of 110 mAh g1and current density of 0.05 A g1in 2000 cycles.

[0080] In various embodiments, PI-DAAQ exhibit specific capacity of 180 mAh g1and 0.05 A g1in 1000 cycles.

[0081] In various embodiments, two novel polyimides (PI) such as PI-COF and PI-DAAQ are synthesized incorporating a redox-active PTCDA as the connecting unit. This approach proves to be effective in enhancing the specific capacity of the synthesized polyimides and this approach enhances the cycling performance of materials in rechargeable Zinc-ion batteries (ZIBs).

[0082] In an embodiment of the present invention, the electrochemical device is aqueous rechargeable zinc-ion battery selected from full cell device or half-cell device.

[0083] In yet another aspect, the present invention provides a half-cell device comprising perylene -based polyimides including PI-COF and PI-DAAQ as a cathode material (108), zinc foil as anode, Gra foil as a current collector, aqueous electrolytes such as 2M Zinc sulphate (ZnSO4), and glass fibre membrane as a separator. The half-cell also includes positive case and negative case along with spacer and spring.

[0084] In yet another aspect, the present invention provides a full-cell device comprising perylene-based polyimides including PI-COF and PI-DAAQ as a cathode material (108), zinc foil as anode, Gra foil as a current collector, aqueous electrolytes such as 2M Zinc sulphate (ZnSO4), and glass fibre membrane as a separator. The full-cell also includes positive case and negative case along with spacer and spring.

[0085] The Na+ionic radius is around -1.02 A (coordination number (CN) = 6 or 4), and Zn2+ionic radius is -0.74 A ((Coordination number CN = 6). Although Zn2+is smaller in radius, its higher charge density leads to stronger electrostatic interactions and a larger solvation shell, making desolvation and insertion more complex than for Na+. The reaction mechanism of the Na ions and Zn ions both are different, as the Na is a monovalent ion and zinc is bivalent as well as solvation energy for the Zn 2+ ion are approximately 450 kJ / mol while for Na-i- ion are 100 kJ / mol. The surface area and porosity of the present cathode material (108) is around or more than 100 m2 / g with a mesoporous nature, which only then facilitates the Zn2+ion movement and electrolyte access, making it feasible for zinc ion battery performance and its working improvement.

[0086] Polyimide materials for aqueous zinc-ion batteries are characterized by distinct X-ray diffraction (XRD) peaks at 20 = 11.7°, 25.7°, and 27.6°, indicating the presence of ordered TT— TT stacking and lamellar packing structures. These reflections suggest a semi-crystalline nature of the materials, which facilitates Zn2+diffusion and intercalation by providing ordered ion pathways and stabilizing the redox-active framework during cycling. Therefore, the presence of XRD peaks at 11.7°, 25.7°, and 27.6° in the material likely indicates a unique semi -crystalline structure not previously reported in the literature. Table 1 indicates the experimental data comparing the new cathode material of the present invention with typical state-of-the-art cathode materials applied in zinc-ion batteries.

[0087]

[0088] EXAMPLES

[0089] The present invention is further explained in the form of the following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Example 1: Material Synthesis In material synthesis, for the synthesis of PI-COF, firstly the perylenetetracarboxylic dianhydride (PTCDA) was hydrolyzed with 2 .0 equivalent of H2O and added to 20 ml of NMP solution in a beaker then melamine dispersed in NMP was dropwise added into the beaker with continuous stirring. After 2 hours of stirring the solution, it was transferred into stainless steel autoclave, and heated for 48 hours at 210° C. After completion of the reaction the reddish-brown color insoluble solids were obtained by washing with methanol, and DI water and dried in a vacuum oven at 100° C. The same procedure was used for the synthesis of PI-DAAQ except for the precursor used in 2,6 diamino anthraquinone in place of melamine. For the synthesis of PI COF, the molar ratio of PTCDA: Melamine is 1:0.8, and for the PI DAAQ, the molar ratio of PTCDA: 2, 6 diamino anthraquinone is 1: 1.

[0090] Example 2: Materials Characterization

[0091] Fig. 1 shows X-ray diffraction (XRD) pattern of the as-prepared PI-COF and PI-DAAQ in comparison with those of the PTCDA monomer. After polymerization with melamine and 2, 6 diamino anthraquinone, the diffraction peaks of PTCDA disappear, while new peaks emerge at 11.7°, 25.7°, and 27.6°. In particular, the signal at 27.6° is assigned to the it- it stacking of the perylene backbones in PI -COF and PI-DAAQ. Fourier transform infrared (FT-IR) spectra were measured to reveal the molecular structure of PI-COF and PI-DAAQ. It is worth noting that the vibration peak of the carbonyl groups (C=O) in PI-COF and PI-DAAQ (1690 cm-1) shifts toward a lower wavenumber relative to that in PTCDA (1760 cm-1), in good agreement with observations. The signal intensity of the amino groups at ~3461 cm-1and 3409 cm-1is significantly attenuated in PI-COF and PI-DAAQ, which indicates a high degree of polymerization. The characteristic vibrations of perylene at ~1600 cm-1and triazine at ~1500 and 1400 cm-1are also observed, which supports their incorporation into the final product.

[0092] The PI-COF and PI-DAAQ product was next studied by microscopic characterization. Field emission scanning electron microscopy (SEM) imaging shows that PIF roughly has a rod shape morphology. Moreover, elemental mapping using energy dispersive spectroscopy (EDS) supports the uniform spatial distribution of C, N, and O species throughout sample, and thereby demonstrates the uniform chemical composition of PI-COF and PI-DAAQ as shown in Figure 2a and 2b. According to Fig. 6 (a to d), PI-DAAQ material exhibits a moderate specific surface area of 90.3 m2g-1compared to the higher surface area of 182m2g1for PI-COF. The enhanced surface area of PI-COF contributes to a greater density of accessible redox-active sites, facilitating improved ion diffusion and charge transfer. Moreover, the ordered, porous framework of PI-COF provides better resistance to structural degradation, making it a more durable and stable cathode material for long-term Zn-ion battery applications. Moreover, the pore size distribution graph shows that both materials exhibit mixed micro and mesoporous structures.

[0093] HRTEM analysis revealed that both PI-DAAQ and PI-COF materials exhibit a rod-shaped morphology. Elemental mapping further confirms the uniform distribution of constituent elements across the structure: carbon (C), nitrogen (N), and oxygen (O). The homogeneous dispersion of nitrogen and oxygen atoms suggests a successful formation of the polyimide framework and supports the structural integrity of the synthesized materials.

[0094] Example 3: Electrochemical Characterization

[0095] The electrochemical performance of PI-COF and PI-DAAQ as the zinc ion battery (ZIB) cathode material was evaluated using standard CR2032 coin cells by pairing it with a metallic Zn disk and filling it with 2M ZnSO4 as the electrolyte (refer, figure 9). The solubility test demonstrates that PI-COF and PI-DAAQ have diminished solubility in the electrolyte after 48 hours (as shown in Fig. 3). This immediately highlights the advantage of polymerized electrode material versus small molecules. The voltage window was 0.2 to 1.8 V.

[0096] Fig. 4a, 4b and 4c show CV curves of PI for the first three cycles. During the cathodic scan, the curve exhibits two broad peaks at 0.58 and 0.38 for PI-COF and 0.72 and 0.51 for PI-DAAQ versus Zn2+ / Zn, and during the reverse anodic scan, a multitude of peaks appear, corresponding to the reverse oxidation process of PI-COF and PI-DAAQ. Importantly, the CV curves after the initial cathodic scan completely retrace each other, which supports the good stability and reversibility of PI-COF and PI-DAAQ during cycling.

[0097] Fig. 5 shows the reversible electrochemistry of PI-COF and PI-DAAQ demonstrated from galv anostatic charge / discharge testing in the potential range between 0.2 to 1.8 V. It is noted that the initial discharge profile is slightly different from those of ensuing cycles, presumably owing to the formation of a solid-electrolyte interface (SEI). Upon discharge, PI-DAAQ delivers a large capacity of ~ 180 mAh g-1at 0.05 A g-1and ~110 mA h g1for PI-COF. At the end of 500 cycles, PI-DAAQ and PI-COF molecules retain a capacity retention of 78% and 99%, respectively, which is larger than those of many other cathode materials find that PI-COF and PI-DAAQ demonstrate excellent cycling stability performance at 1 Ag’1.

[0098] Fig. 7 demonstrates that the PI-COF cathode material possesses outstanding cycling stability, retaining 93% of its initial capacity after 4000 cycles, highlighting its excellent long-term electrochemical suitability for aqueous zinc-ion battery applications.

[0099] Even at a low current rate, both the materials demonstrating high capacity and stable cycling at 100 mAg-1 for 200 cycles support the idea that both PI-COF and PI-DAAQ are not only electrochemically active but also structurally robust for long-term battery viability (refer, figure 8).

[0100] In summary, a porous polyimide PI-COF and PI-DAAQ as high-performance cathode material for ZIBs is reported. The cathode material was prepared via a facile condensation reaction between PTCDA and melamine or 2, 6-diamino anthraquinone. It contained high-density electroactive imide functionalities for Zn2+-ion storage and had diminished solubility in the electrolyte. When used as a ZIB cathode material, PI-COF and PI-DAAQ delivered a large reversible capacity (~ 183 mA h g-1at 0.05 A g-1and 110 at 0.05 A g-1), cycling stability (1000 cycles at 1 A g-1) for both PI-COF and PI-DAAQ materials, which outperformed most existing organic cathode materials of ZIBs as well as results demonstrate that carbonyl group-based organic polymers are sustainable, green and high-performance electrode materials for ZIBs.

[0101] Further, PI-COF material delivers a reversible specific capacity of approximately 108 mAh g’1, while PI-DAAQ achieves a higher specific capacity of around 180 mAh g’1at 0.05 Ag’1. More ver, PI-COF exhibits excellent cycling stability, retaining a capacity retention of 93% over 4000 cycles at 1 A g’1, whereas PI-DAAQ maintains its 76 % capacity retention for up to 1000 cycles under the same current density.

[0102] ADVANTAGES OF THE INVENTION

[0103] 1. The novel cathode materials (108) synthesized using the process provided by the present invention exhibit high specific capacity and excellent cycling stability, making them suitable for use in aqueous zinc-ion batteries (AZIBs). 2. PI-COF and PI-DAAQ delivered a large reversible capacity (~183 mA h g-1at 0.05 A g-1and

[0104] 110 at 0.05 A g“) and cycling stability (1000 cycles at 1 A g-1) for both PI-COF and PI-DAAQ materials.

[0105] 3. The use of organic materials, such as polyimides, offers a cost-effective alternative to traditional inorganic cathode materials, contributing to the affordability of AZIBs. 4. Organic cathode materials are generally environmentally friendly compared to inorganic counterparts, contributing to the development of sustainable energy storage solutions.

[0106] 5. The proposed synthesis method is scalable, allowing for the production of these organic cathode materials in large quantities to meet the demands of grid-scale energy storage systems.

Claims

We Claim:

1. A cathode material for aqueous zinc-ion battery comprising perylene -based polyimide, wherein the cathode material shows X-ray Diffraction peaks at 11.7°, 25.7° and 27.6°, and is a semicrystalline in nature; and wherein a surface area of the cathode material is in the range of 90.3 m2g-1to 182 m2g-1.

2. The cathode material as claimed in claim 1, wherein the cathode material is selected from polyimide diamino anthraquinone (PI-DAAQ) material and polyimide covalent organic framework (PI-COF) material.

3. The cathode material as claimed in claim 1, wherein the cathode material comprises it- it stacking of perylene structural backbone with diamino anthraquinone and / or covalent organic framework, and has uniform spatial distribution of C, N, and O elements; and the cathode material is mesoporous in nature; and the cathode material comprises ordered TT— 7r stacking and lamellar packing structures of perylene-based polyimide.

4. The cathode material as claimed in claim 2, wherein the PLCOF material comprises rod shaped morphology, and has 2D conjugated framework of perylene with covalent organic framework; and the PI-DAAQ material comprises rod shaped morphology, and has 2D linear framework of perylene with diamino anthraquinone.

5. The cathode material as claimed in claim 1, wherein the cathode material is metal-free and recyclable.

6. A process for preparation of the cathode material as claimed in claim 1, comprising: a) hydrolyzing perylenetetracarboxylic dianhydride (PTCDA) with water followed by adding a solvent to obtain PTCDA solution;b) dropwise adding an amine solution into the PTCDA solution of step a) under continuous stirring for a time period in the range of 1-3 hours to obtain a mixture; c) heating the mixture of step b) at temperature in the range of 200-220 °C for a time period in the range of 45-50 hours to obtain insoluble solid material; and d) washing the insoluble solid material of step c) followed by drying to obtain the cathode material.

7. The process as claimed in claim 6, wherein the solvent used in step a) is N-Methylpyrrolidone (NMP), dimethylformamide, N, N- dimethylacetamide, and dimethylsulfoxide or any of mixture thereof; the amine solution comprises an amine in N-Methylpyrrolidone (NMP); the washing of step d) is done using solvent selected from water, methanol, ethanol, propanol and butanol or any of mixture thereof; and the drying of step d) is done in a vacuum oven at temperature in the range of 90-110 °C.

8. The process as claimed in claim 7, wherein the amine is selected from melamine, 2, 6-diamino anthraquinone, diamine, diaminobenzene, diaminonaphthalene, and diamino pyridine.

9. An aqueous zinc-ion battery (100) comprising the cathode material (108) of claim 1.

10. The aqueous zinc-ion battery (100) as claimed in claim 10, wherein the battery further comprises: i) an anode (104), ii) a current collector, iii) an aqueous electrolyte, iv) a separator (106), v) a positive case (114), vi) a negative case (102), viii) a spacer (110), and ix) a spring (112).

11. The aqueous zinc-ion battery (100) as claimed in claim 10, wherein the anode (104) is selected from zinc foiland a preintercalated zinc electrode.

12. The aqueous zinc-ion battery (100) as claimed in claim 10, wherein the current collector is selected from Gra foil, stainless steel foil and titanium foil.

13. The aqueous zinc-ion battery (100) as claimed in claim 10, wherein the aqueous electrolyte is selected from zinc sulphate (ZnSC ), zinc acetate, and zinc trifluromethanesulfonate.

14. The aqueous zinc-ion battery (100) as claimed in claim 10, wherein the separator (106) is selected from glass fiber membrane, polypropylene separator and cellulose separator.

15. The aqueous zinc-ion battery (100) as claimed in claim 10, wherein the positive case (114), and negative case (102) is selected from stainless steel.

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