WO2020188582A1

WO2020188582A1 - Iron ion rechargeable battery and method of making thereof

Info

Publication number: WO2020188582A1
Application number: PCT/IN2019/050373
Authority: WO
Inventors: Sundara Ramaprabhu; Vijaya Kumar Saroja AJAY PIRIYA
Original assignee: Indian Institute of Technology Madras
Current assignee: Indian Institute of Technology Madras
Priority date: 2019-03-20
Filing date: 2019-05-10
Publication date: 2020-09-24
Anticipated expiration: 2021-09-20

Abstract

The invention discloses a rechargeable iron ion battery and a method of charging and discharging the battery. The battery comprises an anode including iron, an iron compound or an alloy thereof, a cathode including a layered metal oxide coated on a current collector, an electrode separator membrane and an iron ion conducting electrolyte in contact with the anode and the cathode. The cathode is coated with slurry containing at least one additive and a binding agent. During charging, de-intercalation of Fe2+ ions from the cathode occurs and the electrolytes causes transport of Fe2+ ions from the cathode to the anode via the electrolyte. During discharging, electroplating of Fe2+ ions occurs at the anode and the ions from the anode migrate towards the cathode. The cathode accommodates the Fe2+ ions within the layered metal oxide structure. The battery has a cyclic stability with 40 - 50% capacity retention.

Description

IRON ION RECHARGEABLE BATTERY AND METHOD OF MAKING THEREOF

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims priority to Indian patent application No. 201941010965 entitled IRON ION RECHARGEABLE BATTERY AND METHOD OF MAKING THEREOF filed on March 20, 2019.

FIELD OF THE INVENTION

[0002] The present invention relates to a rechargeable iron ion battery and a method of fabricating the battery.

DESCRIPTION OF THE RELATED ART

[0003] Rechargeable energy storage is merely the practical and best solution for mitigating the problem between energy generation and demand. Rechargeable batteries are widely used in portable electronic devices, hybrid electric vehicles. In the past centuries, several battery systems have been developed, but only a few have been demonstrated in large-scale applications. Reversible electrochemical intercalation of metal ions has laid the foundation of rechargeable batteries. Currently, lithium ion battery is the choice of power source for portable electronic devices. However, the cost of lithium and its limited availability urges us to move towards an alternative cost-effective storage technology for large-scale applications.

[0004] Several other metals like sodium, iron, potassium, calcium, magnesium, aluminium and zinc are highly abundant and can be used as a substitute for lithium to reduce the cost of the device. Moreover, when compared to monovalent ion storage as in lithium ion battery, multivalent ion storage offers advantages like increase in energy density of intercalation-based electrodes. This is due to the fact that only half the number of ions is sufficient to intercalate for the same number of electrons transferred. This promises the increase in energy density for the multivalent metal ion batteries compared to monovalent ion battery. Iron, is particularly attractive as a raw material for batteries due to its varied advantages such as globally abundant, relatively inexpensive, eco-friendly and it can be recycled easily. Rechargeable Iron-based batteries such as nickel-iron and iron-air are predominant in the electrical energy storage systems. Nickel-iron battery is well known for their tolerance to overcharge and over-discharge.

[0005] US8758948B2 discloses an iron-air rechargeable battery having a composite electrode including an iron electrode and hydrogen electrode with an air electrode spaced between the iron electrode and the electrolyte to provide the contact. However, during the charging process, the formation of iron oxides due to the hydrogen evolution reaction may lead to loss of water from the electrolyte. This may result in poor columbic efficiency and poor discharge rate capability. The limitations of iron air battery further includes self discharge, the occurrence of degrading iron oxidation reactions.

[0006] W02013090680A2 discloses a rechargeable metal anode cell comprising a metal electrode, an air contacting electrode and an aqueous electrolyte separating both, wherein the metal electrode is zinc or magnesium and the air contacting electrode is carbon or a polymer. However, zinc and magnesium batteries are reported to have poor cycle life and low energy density. Due to the strong interaction between the doubly charged Mg²⁺ ions and the host matrix, most of the conventional intercalation cathodes suffer from low capacity, high voltage hysteresis, and low energy density. These batteries may lose volume over time as the charging cycle leads to the formation of alloys and the battery loses the ability to charge.

[0007] US9368788B2 discloses a coated iron electrode comprises an iron electrode of a multilayered coating on a single conductive substrate and nickel cathode. The iron based electrode is used in alkaline rechargeable batteries particularly as a negative electrode in Ni- Fe battery. However, Ni-Fe batteries have several limitations like high cost of manufacturing, high self-discharge rate, lower energy density and lower specific power compared to lead- acid batteries making them less efficient. [0008] As compared to other metals, low cost iron is mostly preferable due to its inexhaustible resources, multiple oxidation states, very less tendency to form dendrites during the process of repeated cycling and easy recycling. The advantageous feature of iron is its divalent nature, global availability and high specific capacity of iron up to 960mAhg ¹ hence it is advantageous to use only Fe metal for the rechargeable batteries. However, the redox potential of Fe/Fe²⁺ is - 0.41 V, which is much higher than lithium metal (-3.01 V) and due to this high redox potential of Fe/Fe²⁺ there is a decrease in energy density. Since the redox potential is very high when compared to lithium, there is a need to overcome this limitation.

SUMMARY OF THE INVENTION

[0010] The present invention discloses a rechargeable iron ion battery and a method of charging and discharging the battery.

[0011] In one embodiment, a rechargeable iron ion battery is disclosed herein. The rechargeable battery comprises an anode including iron, an iron compound or an alloy thereof, a cathode including a layered metal oxide coated on a current collector, an electrode separator membrane and an iron ion conducting electrolyte in contact with the anode and the cathode. The cathode is coated with slurry containing at least one conducing additive and a binding agent. The iron ion conducting electrolyte transports Fe²⁺ ions between the anode and the cathode.

[0012] In various aspects, the anode is selected from a group of mild steel, iron, iron- carbon or oxides of iron. In various embodiments, the layered metal oxide of the cathode includes one or more of molybdenum, manganese, or vanadium oxide. In various embodiments, the cathode accommodates the Fe²⁺ ions within the layered metal oxide structure.

[0013] In various aspects, the separator is selected from one of polymers including polyolefin, polyethylene, propylene, polytetrafluoroethylene (PTFE) or a glass fiber membrane.

[0014] In various aspects, the electrolyte includes ether or carbonate based solvent comprising at least one selected from the group of tetraethylene glycol dimethyl ether (TEGDME), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and /or combinations thereof.

[0015] In some aspects, the current collector includes a conductive metal, conductive polymers, carbon or an alloy thereof in the form of a conductive screen, a fabric, foam, a sheet, a mesh, or combinations thereof. [0016] In various aspects, the binding agent includes polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyethersulfone, ethylene-propylene -diene copolymer (EPDM), styrene-butadiene rubber (SBR) or carboxymethyl cellulose (CMC). In some embodiments, the conducting additive includes at least one of carbon nanotubes, carbon nanofibers, graphene, acetylene black, conductive graphite, activated carbon, pyrolytic graphite or vitreous carbon.

[0017] In one aspect of the disclosure, the cathode includes 75% of vanadium pentoxide (V2O5) with a slurry coating of 15% of multiwalled carbon nanotubes (MWCNT) and 10% of polyvinylidene fluoride.

[0018] In some aspects, the battery has a specific capacity of 100 - 200 mAhg ¹ and a current density of 30 - 100 mAg ¹. In various embodiments, the battery has a discharge voltage of 1 - 1.5 V. In some aspects, the battery has a cyclic stability with 40 - 50% capacity retention. In various aspects, the battery is reversible in aqueous and non-aqueous electrolytes.

[0019] In one embodiment of the disclosure, a method for charging or discharging a battery is disclosed. The method includes providing an iron metal or an alloy anode, providing a layered metal oxide coated on a current collectors as a cathode, providing an electrode separator membrane between the anode and the cathode, providing an electrolyte between electrodes to form a rechargeable battery for storing the energy and causing transport of Fe²⁺ ions from the cathode to the anode via the electrolyte while charging and transport of Fe²⁺ ions from the anode to the cathode via the electrolyte while discharging.

[0020] In various aspects, the cathode is coated with slurry including at least one conducting additive and a binding agent. In various aspects, the cathode accommodates the Fe²⁺ ions within the layered metal oxide structure.

[0021] This and other aspects are disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention has other advantages and features which will be more readily apparent from the following detailed description of the invention and the appended claims, when taken in conjunction with the accompanying drawings, in which:

[0023] FIG. 1A shows a schematic of the Iron ion rechargeable battery.

[0024] FIG. IB illustrates the ion transport during discharging and FIG. 1C illustrates the ion transport during charging.

[0025] FIG. 2 illustrates the method of fabricating iron ion rechargeable battery.

[0026] FIG. 3 shows X-ray diffraction pattern of V2O5 indicating high degree of crystallization.

[0027] FIG. 4A and FIG. 4B illustrates FESEM images of V₂0₅ and FIG. 4C and FIG. 4D illustrates TEM images of V2O5.

[0028] FIG. 5A shows XRD pattern of mild steel and FIG. 5B shows SEM image of mild steel.

[0029] FIG. 6A shows galvanostatic charge and discharge profile for iron ion battery using mild steel anode - V2O5 supported on SS foam cathode assembled inside glove box.

[0030] FIG. 6B shows E vs. t plot of cell for iron ion battery using mild steel anode - V2O5 supported on SS foam cathode assembled inside glove box.

[0031] FIG. 7A shows cyclic stability curve of iron ion battery using mild steel anode - V2O5 supported on SS foam cathode assembled inside glove box.

[0032] FIG. 7B shows cyclic voltammetry curve for reversible electroplating and electro stripping of pure mild steel. [0033] FIG. 8A shows galvanostatic charge and discharge profile for iron ion battery using mild steel anode - V2O5 / MWCNT - carbon paper cathode assembled inside glove box.

[0034] FIG. 8B shows cyclic stability curve of cell for iron ion battery using mild steel anode - V2O5 / MWCNT - carbon paper cathode assembled inside glove box.

[0035] FIG. 9 shows galvanostatic charge discharge profile for iron ion battery using mild steel anode - V2O5 / MWCNT - carbon paper cathode assembled in ambient condition.

[0036] FIG. 10A shows galvanostatic charge discharge profile for iron ion battery using mild steel anode - V2O5 / MWCNT - SS foam cathode assembled in ambient condition.

[0037] Fig. 10B shows cyclic stability for iron ion battery using mild steel anode - V2O5 / MWCNT - SS foam cathode assembled in ambient condition.

[0038] FIG. 11 illustrates the operation of iron ion battery using M0O3 / multiwalled carbon tubes as the cathode and mild steel anode assembled inside glove box.

[0039] Referring to the drawings, like numbers indicate like parts throughout the views.

DETAILED DESCRIPTION

[0040] While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from its scope.

[0041] Throughout the specification and claims, the following terms take the meanings explicitly associated herein unless the context clearly dictates otherwise. The meaning of "a", "an", and "the" include plural references. The meaning of "in" includes "in" and "on." Referring to the drawings, like numbers indicate like parts throughout the views. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or inconsistent with the disclosure herein.

[0042] The present invention in its various embodiments discloses an ambient temperature rechargeable iron ion battery and a method of charging or discharging the battery.

[0043] In one embodiment of the disclosure, a rechargeable battery 100 is disclosed herein. FIG. 1A shows a schematic of the Iron ion rechargeable battery. The rechargeable battery comprises an anode 110 made of iron, an iron compound or an alloy thereof, a cathode 120 having a layered metal oxide coated on a current collector. The electrodes may be separated by a porous electrode separator membrane 130 and the cell is provided with an iron-ion conducting electrolyte 140 in contact with the anode and the cathode, through the electrode separator membrane.

[0044] In various embodiments, the layered metal oxide on the cathode acts as a potential intercalation host for Fe²⁺ ions and the intercalation of multivalent ions occurs between the layers of metal oxide. The iron-ion conducting electrolyte 140 transports Fe²⁺ ions between the anode and the cathode or vice versa. During discharge, electro stripping of Fe²⁺ ions occurs at the anode 110 and Fe²⁺ ions from the anode migrate towards the cathode through the electrolyte while electrons flow through the external circuit. FIG. IB illustrates the ion transport during discharging. In the cathode 120, Fe²⁺ ions intercalate between the layers of metal oxide. The cathode accommodates the Fe²⁺ ions within the layered metal oxide structure. During charging, de-intercalation of Fe²⁺ ions from the cathode occurs and the electroplating of Fe occurs at the anode. FIG. 1C illustrates the ion transport during charging. In various embodiments, the iron ion battery works on the principle of shuttling of Fe²⁺ ions between the cathode and the anode.

[0045] In various embodiments, the anode 110 may be any iron containing material such as mild steel, iron, iron-carbon or oxides of iron. In some embodiments, the intercalation host for Fe²⁺ ions at the cathode includes various metal oxides like M0O₃, Na₃V₂(P0₄)₃, MnCF or other metal doped V₂O₅ on the current collector. In some embodiments, the cathode is configured with layered vanadium oxide as the intercalation host for Fe²⁺ ions due to its multiple oxidation states and high theoretical specific capacity.

[0046]

[0047] In various embodiments, the cathode or current collector includes a conductive metal, conductive polymers, carbon or an alloy in the form of conductive screen, a fabric, foam, a sheet, a mesh or any combinations thereof. In some embodiments, the conductive metal of the current collector includes stainless steel (SS) or carbon supported on foam, mesh, sheets or paper.

[0048] In various embodiments, the separator is a porous membrane selected from a polymer or other chemically inert material such as polyolefin, polyethylene, propylene, polytetrafluoroethylene (PTFE) or glass fiber membrane.

[0049] In various embodiments, the iron-ion battery is operable in aqueous or non- aqueous electrolytes. In some embodiments the electrolyte is Fe(OC>₄)₂ dispersed in a solvent. In various embodiments, the electrolyte includes ether or carbonate based solvent comprising tetraethylene glycol dimethyl ether (TEGDME), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) or combinations thereof.

[0050] In various embodiments the cathode 120 is coated with slurry including at least one conducing additive and a binding agent. The conducting additive aids in the better transport of the electrons and binder is added for holding the electrode material to the current collector. In various embodiments the conducting additive includes carbon nanotubes, carbon nanofibers, graphene, acetylene black, conductive graphite, activated carbon, pyrolytic graphite or vitreous carbon or mixtures thereof. In various embodiments, the binding agent includes polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyethersulfone, ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR) or carboxymethyl cellulose (CMC).

[0051] In one embodiment of the disclosure, a method 200 for charging or discharging a battery is disclosed herein. FIG. 2 illustrates a method for charging or discharging an iron ion rechargeable battery. The method 200 includes providing an iron metal or an alloy anode 201, providing a layered metal oxide coated on a current collector as a cathode 202, coating the cathode with a slurry of a conducting additive and a binding agent 203, providing an electrode separator membrane between the anode and the cathode 204 and providing an electrolyte between the electrodes to form a rechargeable battery for storing the energy 205. During charging, de-intercalation of Fe²⁺ ions from the cathode occurs and the electrolytes causes transport of Fe²⁺ ions from the cathode to the anode via the electrolyte. During discharging, electroplating of Fe²⁺ ions occurs at the anode and the ions from the anode migrate towards the cathode through the electrolyte. The cathode accommodates the Fe²⁺ ions within the layered metal oxide structure.

[0052] In various embodiments, the high redox potential of Fe/Fe²⁺ is compensated by the shuttling of divalent Fe²⁺ metal ionsThe insertion of Fe²⁺ ions into an intercalation host is feasible due to small ionic radius of 77pm which does not impose any volume expansion in the intercalation host compared to other multivalent ions thus showing excellent durability of the cell. In various embodiments, the rechargeable battery results in the reversible electroplating and stripping of Fe in aqueous and non-aqueous electrolytes.

[0053] In various embodiments, the rechargeable iron ion battery (FIB) delivers a specific capacity of 100-200 mAhg ¹ at a current density of 30-100 mAg ¹. In various embodiments, the battery exhibits cyclic stability with a specific capacity of 125 mAh ^{_ 1} at the end of 80 cycles which is about 47 % capacity retention.

[0054] In various embodiments, for the battery with the reversible specific capacity of 100 - 200 mAhg ¹ and an average discharge voltage of 1 - 2 V the energy density obtained is about 220 Whkg ¹. In some embodiments, the battery has an open circuit potential of 1 - 1.5V.

[0055] In some embodiments, the battery has a discharge voltage of 1 - 1.5 V. In some embodiments, the battery has a cyclic stability with 40 - 50% capacity retention. In various embodiments, the rechargeable iron ion battery is reliable and inexpensive.

[0056] EXAMPLES

[0057] Example 1: Fabrication of iron-ion battery and performance analysis

[0058] An exemplary iron-ion battery was constructed using two electrodes with anode as mild steel and layered metal oxide as the cathode. V2O5 was chosen as the intercalation host due to its layered structure facilitating the intercalation of Fe²⁺ ions. For the fabrication of the cell, current collector was coated with slurry and the cathode was prepared using the doctor blade technique. The slurry was prepared using 75 % of V2O5, 15 % of multiwalled carbon nanotubes as conducing additive and 10 % of polyvinylidene fluoride as binder. FIG. 3 illustrates X-ray diffraction pattern of V2O5 that clearly indicates high degree of crystallization. All the diffraction peaks of V2O5 are assigned to the orthorhombic crystal structure of V2O5. FIG. 4A and FIG. 4B illustrates the field emission scanning electron microscopy (FESEM) images representing flake like morphology with interconnected structures. The interconnected structure helps to facilitate better migration of electrolyte ions.

-l i The flake like morphology is further confirmed using transmission electron microscopy (TEM) images. FIG. 4C and FIG. 4D shows TEM images of V2O5.

[0059] FIG. 5A illustrates the XRD pattern of mild steel that indicates the alpha phase of Fe. The peak indexed corresponds to the cubic crystal structure of Fe. The SEM image of surface of mild steel is shown in FIG. 5B and it can be inferred from the figure that the surface is free of pits or holes after surface polishing.

[0060] Mild steel or iron metal or carbon inserted iron was polished using sand paper till the surface of the metal becomes lustrous. The electrolyte used was 1M of Fe(C104)2 in tetraethylene glycol dimethyl ether (TEGDME) and glass fiber membrane was used as the separator. The current collector used was Stainless steel or carbon paper in the form of a sheet, mesh, foam or paper. The coated electrode was then dried under vacuum oven overnight. The obtained electrode was used for the fabrication of the battery. The iron-ion battery was developed in CR 2032 coin cells and the fabrication of the cell was done inside the argon filled glove box and in ambient conditions.

[0061] Example 2: Iron ion battery using Mild steel anode and V2O5 supported on SS foam as cathode

[0062] Electrochemical measurement of iron ion battery assembled in CR 2032 coin cells using the galvanostatic charge discharge studies was done. The galvanostatic charge and discharge profile for iron ion battery using mild steel anode, V2O5 supported on SS foam cathode assembled inside glove box was plotted as shown in FIG. 6A. The figure represents the galvanostatic charge and discharge studies in the potential range of 0 to 2.1 V at different current densities like 30mAg^_1, 50mAg^_1, lOOmAg ¹ and 200mAg^_1. The charge and discharge profile indicates a plateau in the charging and two plateaus in the discharging region. The discharging plateaus indicate the intercalation of divalent iron ions in the interlayer of V2O5 structure and the charging plateau indicates the de-intercalation of Fe²⁺ ions. The cell delivers a specific capacity of 200mAhg ¹ at a current density of 30mAg^_1. FIG. 6B represents Potential vs. time (E vs. t) plot of iron ion battery at a current density of 30 mA g , which shows a stable potential for about 1000 h.

[0063] FIG. 7A illustrates cyclic stability curve of iron ion battery using mild steel anode - V₂O₅ supported on SS foam cathode assembled inside glove box at a current density of 30 mAg ¹. It can be inferred from the figure that the cell exhibits a cyclic stability with a specific capacity of 125 mAhg ¹ at the end of 60 cycles which is about 47 % capacity retention. FIG. 7B illustrates the reversible electro stripping and electroplating of Fe²⁺ ions at the anode using cyclic voltammetry curve for pure mild steel. The process of reversible electroplating and electro stripping of Fe was confirmed using electrochemical study in a three electrode system. The electrode measurement was done using copper sheet as the working electrode, platinum wire as the counter electrode and mild steel as the reference electrode in iron conducting ether based electrolyte (TEGDME). The cyclic voltammetry was carried out in the potential range of -1 to 1 V at the scan rate of 10 mVs ¹. The redox peaks in the cathodic and anodic scan represents reversible electro deposition of Fe²⁺ ions in the anode metal. This confirmed the reversible iron ion (Fe²⁺ ions) storage in the battery.

[0064] Example 3: Iron ion battery using Mild steel anode and V2O5 supported on carbon paper as cathode

[0065] Iron ion battery using mild steel anode and V₂O₅ supported on carbon paper as cathode was assembled inside glove box and electrochemical measurement was done. FIG. 8A represents the galvanostatic charge discharge profile of iron ion battery. The charge discharge profile is similar to profile as shown in FIG. 6A. This indicates that the use of different current collector does not affect the performance of the battery. The discharge specific capacity obtained is about 135 mAhg ¹ at a current density of 100 mAg ¹. FIG. 8B represents the cyclic stability at the same current density.

[0066] The fabricated battery was assembled in ambient condition without the use of argon filled glove box. FIG. 9 represents the galvanostatic charge discharge profile for iron ion battery. The charge discharge profile shows similar charge and discharge plateaus signify that assembly of battery did not affect the performance of the battery and represents the safety of the battery.

[0067] Example 4: Iron ion battery using Mild steel anode and V2O5 supported on stainless steel current collector as cathode

[0068] Iron ion battery using mild steel anode and V2O5 supported on stainless steel current collector as cathode was assembled in ambient condition. FIG. 10A shows galvanostatic charge discharge profile for iron ion battery. The charge-discharge profile shows reversible divalent metal ion storage with the specific capacity of 130 mAhg ¹ at a current density of 30 mAg ¹. This signifies that the battery can be assembled and operated in ambient condition without the use of expensive inert gas filled chamber. Fig. 10B shows cyclic stability for iron ion battery assembled in ambient condition.

[0069] Example 5: Iron ion battery using Mild steel anode and M0O3 as cathode

[0070] FIG. 11 shows the operation of iron ion battery using M0O3 as cathode and mild steel as the anode assembled inside glove box. The cell delivered a specific capacity of 50mAhg^_1 at a current density of 30 mAg ¹.

Claims

WE CLAIM:

1. A rechargeable battery ( 100) comprising :

an anode (110) comprising iron, an iron compound or an alloy thereof;

a cathode (120) comprising a layered metal oxide coated on a current collector, wherein the cathode is coated with slurry comprising at least one conducting additive and a binding agent;

an electrode separator membrane (130); and

an iron-ion conducting electrolyte (140) in contact with the anode (110) and the cathode (120) and configured to transport Fe²⁺ ions between the anode and the cathode or vice versa.

2. The battery of claim 1, wherein the anode (110) is selected from a group of mild steel, iron, iron-carbon or oxides of iron.

3. The battery of claim 1, wherein the layered metal oxide of the cathode (120) comprises one or more of molybdenum, manganese, or vanadium oxide.

4. The battery of claim 3, wherein the cathode (120) is configured to accommodate the Fe²⁺ ions within the layered metal oxide structure.

5. The battery of claim 1, wherein the separator (130) is selected from one of polymers comprising polyolefin, polyethylene, propylene, polytetrafluoroethylene (PTFE) or a glass fiber membrane.

6. The battery of claim 1, wherein the electrolyte (140) comprises ether or carbonate based solvent comprising at least one selected from the group of tetraethylene glycol dimethyl ether (TEGDME), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and /or combinations thereof.

7. The battery of claim 1, wherein the current collector comprises a conductive metal, conductive polymers, carbon or an alloy thereof in the form of conductive screen, a fabric, foam, a sheet, a mesh, or combinations thereof.

8. The battery of claim 1, wherein the binding agent comprises polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyethersulfone, ethylene-propylene- diene copolymer (EPDM), styrene-butadiene rubber (SBR) or carboxymethyl cellulose (CMC).

9. The battery of claim 1, wherein the conducting additive comprises at least one of carbon nanotubes, carbon nanofibers, graphene, acetylene black, conductive graphite, activated carbon, pyrolytic graphite or vitreous carbon.

10. The battery of claim 1, wherein the cathode comprises 75% of vanadium pentoxide (V2O5) with a slurry coating of 15% of multiw ailed carbon nanotubes and 10% of polyvinylidene fluoride.

11. The battery of claim 1, wherein the battery has a specific capacity of 100 - 200 mAh g ¹ and a current density of 30 - 100 mAg ¹.

12. The battery of claim 1, wherein the battery has a discharge voltage of 1 - 1.5 V.

13. The battery of claim 1, wherein the battery has a cyclic stability with 40 - 50% capacity retention.

14. The battery of claim 1, wherein the battery is reversible in aqueous and non-aqueous electrolytes.

15. A method for charging or discharging a battery, comprising:

providing an iron metal or an alloy anode;

providing a layered metal oxide coated on a current collector as a cathode; providing an electrode separator membrane between the anode and the cathode; providing an electrolyte between electrodes to form a rechargeable battery for storing the energy; and

causing transport of Fe²⁺ ions from the cathode to the anode via the electrolyte while charging and transport of Fe²⁺ ions from the anode to the cathode via the electrolyte while discharging.

16. The method of claim 15, wherein the cathode (120) is coated with slurry comprising at least one conducting additive and a binding agent.

17. The method of claim 15, wherein the cathode (120) is configured to accommodate the Fe²⁺ ions within the layered metal oxide structure.