ZINC BASED RECHARGEABLE REDOX STATIC ENERGY STORAGE DEVICE

Abstract

A zinc based rechargeable redox static energy storage device includes a cathode including a carbon material—binder composition and an anode including carbon material—Zinc material—binder composition both infused with an eutectic electrolyte comprising one or more inorganic transition metal salt(s) of zinc, one or more Metal hydroxide(s) and eutectic solvent comprising derivative(s) of methanesulfonic acid, ammonium salt(s) and hydrogen bond donor(s); a separator separating the cathode and anode so that the ion exchange carries in between the cathode and anode through ionic permeability; and current collector connected with the cathode and anode respectively.

Claims

1. A zinc based rechargeable redox static energy storage device comprising: a cathode pre-infused with a eutectic electrolyte in ratio ranging between 0.5-1.5:2-5; an anode pre-infused with the eutectic electrolyte in ratio ranging between 0.5-1.5:2-5; a first current collector connected to the cathode; a second current collector connected to the anode; and a separator separating the cathode and anode, wherein the separator is configured so that an ion exchange carries in between the cathode and anode through ionic permeability.

2. The zinc based rechargeable redox static energy storage device of claim 1, wherein: the cathode comprises a composition of a first carbon material and a first binder in weight ratio maintained between 80-99.9:0.1-20; the anode comprises a composition of a second carbon material, a Zinc material, and a second binder in weight ratio maintained between 80-90:10-15.9:0.1-10; wherein the first and second carbon materials are selected from the group consisting of conductive carbon black, graphite, carbon particles, carbon nanoparticles, woven or non-woven carbon cloth, carbon felt, carbon paper, carbon rod, and combination thereof; wherein the first and second binders are selected from the group consisting of PTFE, PVDF, SBR, CMC, and PVA; wherein the Zinc material is selected from the group consisting of Zinc powder, Zinc Dust, and Zinc foil; wherein the eutectic electrolyte comprises one or more inorganic transition metal salt(s) of zinc selected from the group consisting of Zinc Chloride, Zinc Acetate, and Zinc Methanesulfonate, Zinc Sulphate, Zinc triflate; one or more salt(s) of metal(s) selected from the group consisting of manganese, nickel, titanium and copper metal with sulphate anions, methane sulfonate anions, halides anions including chloride, bromide, and organic salts of transition metal ions with anions selected from the group consisting of acetate, oxalates, formates, phosphinates, lactate, malate, citrate, benzoate, and ascorbate; one or more Metal hydroxide(s) selected from the group consisting of sodium hydroxide, potassium hydroxide, aluminum hydroxide, zinc hydroxide, calcium hydroxide, cesium hydroxide, magnesium hydroxide, and iron hydroxide; wherein one or more inorganic transition metal salt(s) of zinc, one or more salt(s) of metal(s), and one or more Metal hydroxide(s) in molar concentration range 0.1-3:0.1-3:0.05-1 are mixed to a eutectic solvent comprising one or more derivative(s) of methanesulfonic acid selected from its salts with various metal ions selected from the group consisting of manganese, zinc, cerium, nickel, titanium, copper, sodium, potassium and calcium; one or more ammonium salt(s) having general formula NH4X, where X is selected from the group consisting of chloride, methanesulfonate, acetate, sulphate, triflate, and trimethanesulfonate; and one or more hydrogen bond donor(s) selected from the group consisting of urea, thiourea, glycerol, oxalic acid, acetic acid, ethylene glycol, acetamide, benzamide, adipic acid, benzoic acid, and citric acid; wherein the molar ratio of derivative(s) of methanesulfonic acid, ammonium salt(s) and hydrogen bond donor(s) is in the range 0.5-3: 2-7:8-13.

3. The zinc based rechargeable redox static energy storage device of claim 2, wherein the first current collector is selected from the group consisting of titanium, and carbon material, and the second current collector is selected from the group consisting of titanium, carbon material, and zinc material.

4. The zinc based rechargeable redox static energy storage device of claim 3, wherein the separator comprises material selected from the group consisting of micro porous PVC, micro porous poly propylene, absorptive glass mat, and cellulose filter paper.

5. The zinc based rechargeable redox static energy storage device of claim 4, wherein the thickness ratio of the anode and cathode ranges in between 2-10:1-5.

6. The zinc based rechargeable redox static energy storage device of claim 5, having a C rating of 0.2-5.

7. The zinc based rechargeable redox static energy storage device of claim 6, having a cycle life ranging between 3000 to 10000 cycles.

8. A method of preparing a zinc based rechargeable redox static energy storage device, said method comprising: infusing a cathode with a eutectic electrolyte in ratio ranging between 0.5-1.5:2-5; infusing an anode with the eutectic electrolyte in ratio ranging between 0.5-1.5:2-5; connecting a first current collector to the cathode; connecting a second current collector connected to the anode; and separating the cathode from the anode with a separator so that an ion exchange carries in between the cathode and the anode through ionic permeability.

9. The zinc based rechargeable redox static energy storage device of claim 1, wherein the first current collector is selected from the group consisting of titanium, and carbon material, and the second current collector is selected from the group consisting of titanium, carbon material, and zinc material.

10. The zinc based rechargeable redox static energy storage device of claim 9, wherein the separator comprises material selected from the group consisting of micro porous PVC, micro porous poly propylene, absorptive glass mat, and cellulose filter paper.

11. The zinc based rechargeable redox static energy storage device of claim 9, wherein the thickness ratio of the anode and cathode ranges in between 2-10:1-5.

12. The zinc based rechargeable redox static energy storage device of claim 9, having a C rating of 0.2-5.

13. The zinc based rechargeable redox static energy storage device of claim 9, having a cycle life ranging between 3000 to 10000 cycles.

14. The zinc based rechargeable redox static energy storage device of claim 1, wherein the separator comprises material selected from the group consisting of micro porous PVC, micro porous poly propylene, absorptive glass mat, and cellulose filter paper.

15. The zinc based rechargeable redox static energy storage device of claim 1, wherein the thickness ratio of the anode and cathode ranges in between 2-10:1-5.

16. The zinc based rechargeable redox static energy storage device of claim 1, having a C rating of 0.2-5.

17. The zinc based rechargeable redox static energy storage device of claim 1, having a cycle life ranging between 3000 to 10000 cycles.

18. The zinc based rechargeable redox static energy storage device of claim 17, wherein the separator comprises material selected from the group consisting of micro porous PVC, micro porous poly propylene, absorptive glass mat, and cellulose filter paper.

19. The zinc based rechargeable redox static energy storage device of claim 18, wherein the thickness ratio of the anode and cathode ranges in between 2-10:1-5.

20. The zinc based rechargeable redox static energy storage device of claim 19, having a C rating of 0.2-5.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0021] FIG. 1 is an exploded view of one embodiment according to present invention;

[0022] FIG. 2 shows a scan rate of 5 mV/s, the cyclic voltammetry curve of test device. At a possible range of 1-2.2V, a pair of well-defined peaks could be seen. The ratio of oxidation and reduction is ˜1 indicating highly reversible reaction;

[0023] FIG. 3 shows XRD pattern of cathode of test devices A and B at 100% and 0% state of charge respectively after removing carbon peaks. At 0% SOC there are no obvious peaks except for titanium current collector peaks while at 100% SOC there are Manganese Dioxide peaks;

[0024] FIG. 4 shows Galvanostatic charge-discharge profile of test device. Two voltage plateaus at around 1.5 V and 1.4 V represents charging and discharging process, respectively;

[0025] FIG. 5 shows cycling of the test device at a constant current, the test device's charge-discharge behavior. Both profiles show a steady increase in discharge capacity as the cycle life increases;

[0026] FIG. 6 shows Galvanostatic charge-discharge profile of test device at constant voltage 1.7 V charge—constant current discharge (CV-CC) condition;

[0027] FIG. 7 shows Galvanostatic charge-discharge profile of test device at different current rate, i.e., C/7, C/4, 1C, 5C. High columbic efficiency and low polarization is observed throughout the current range;

[0028] FIG. 8 shows the cycle performance—Coulombic efficiency and discharge capacity of prepared test device in different temperature of 15 C (Lower Dot) and 30 C (Upper Dot);

[0029] FIG. 9 shows Cycle life, Coulombic efficiency of the Zinc Redox battery test device at 3C rate. The Zinc Redox battery exhibits excellent cycling stability. Close to 95% of the maximum discharge capacity is maintained after prolong cycling; and

[0030] FIG. 10 shows Cycle life, Coulombic efficiency of the Zinc Redox battery test device at 5C rate. The Zinc Redox battery exhibits excellent cycling stability, even at high rates.

DETAILED DESCRIPTION OF THE DRAWINGS

[0031] The present invention discloses a zinc based rechargeable redox static energy storage device (1) which_works on redox principle. The components used in the preparation of the device (1) are eco-friendly, non-toxic and non-flammable. The device, according to the present invention, is recyclable.

I. Definitions

[0032] For purposes of interpreting the specification and appended claims, the following terms shall be given the meaning set forth below:

[0033] The term “redox” shall refer to chemical reaction in which oxidation and reduction changes can occur by losing and gaining electrons for example Mn.sup.2+ ion is oxidized to manganese dioxide, Manganese dioxide is reduced to Mn.sup.2+ ion.

[0034] The term “static energy storage device” shall mean an energy storage device with physically non-flowing or non-moving electrolyte or cathode or anode materials.

[0035] The term “solvent” shall refer to a liquid medium capable of dissolving other substance(s). The “eutectic electrolyte” shall refer to an electrolyte solution that comprises ions, but does not use water as the solvent. It generally contains eutectic solvent and ions, atoms or molecules that have lost or gained electrons, and is electrically conductive.

[0036] The term “carbon material” shall refer to carbon-containing material or carbon-containing compound having at least 98% carbon. Examples includes but not limited to conductive carbon black, carbon particles, carbon nanoparticles, woven or non-woven carbon cloth, carbon felt, carbon paper, carbon rod, and combination thereof.

[0037] The binder shall refer to a substance that holds two or more materials together. Examples includes but not limited to PTFE, PVDF, SBR, CMC, PVA.

[0038] The zinc material shall refer to various form of zinc metal. Examples includes but not limited to Zinc powder, Zinc Dust, Zinc foil.

[0039] The term “separator” shall refer to a permeable membrane between anode and cathode and allows ion exchange between the electrodes without short circuiting the device. Examples includes but not limited to micro porous PVC, micro porous poly propylene, absorptive glass matt, cellulose filter paper.

[0040] The term “current collectors” shall refer to material used for carrying out conduction of electron through electrodes.

[0041] When referring to the concentration of components or ingredients for electrolytes, Mols shall be based on the total volume of the electrolyte.

II. Description

[0042] Reference is hereby made in detail to various embodiments according to present invention, examples of which are illustrated in the accompanying drawings and described below. It will be understood that invention according to present description is not intended to be limited to those exemplary embodiments. The present invention is intended to cover various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the claims.

[0043] The zinc based rechargeable redox static energy storage device according to present invention comprising a cathode pre-infused with an eutectic electrolyte in ratio ranging between 0.5-1.5:2-5; an anode pre-infused with the eutectic electrolyte in ratio ranging between 0.5-1.5:2-5; wherein the cathode is connected to a current collector; wherein anode is connected to a current collector; a separator separating the cathode and anode so that the ion exchange carries in between the cathode and anode through ionic permeability. In formation of cathode (2), carbon material is homogenously mixed with the binder in the weight ratio ranging between 80-99.9:0.1-20. The carbon material—binder composition is infused with eutectic electrolyte in wt. ratio ranging between 0.5-1.5:2-5 forming a clay-kind paste. The paste is shaped to be used as cathode (2). The cathode (2) so prepared is termed as “cathode pre-infused with the eutectic electrolyte”.

[0044] In formation of anode (3), carbon material is homogenously mixed with Zinc material and the binder in weight ratio ranging between 80-90:10-15.9:0.1-10. The carbon material—Zinc material—binder composition is infused with eutectic electrolyte in wt. ratio ranging between 0.5-1.5:2-5 forming a clay-kind paste. Alternatively, anode (3) is formed by homogenously mixing carbon material with the binder. The carbon material—binder composition is infused with eutectic electrolyte in wt. ratio ranging between 0.5-1.5:2-5 forming a clay-kind paste. Instead of homogenously mixing zinc material to carbon material—binder composition, it is used in from of zinc foil in proportionate weight ratio maintaining carbon material—Zinc material—binder weight ratio ranging between 80-90:10-15.9:0.1-10. The paste is shaped with zinc foil ranging to be used as anode (3). carbon material—Zinc material—binder composition is shaped to be used as anode (3). The anode (3) so prepared is termed as “anode pre-infused with the eutectic electrolyte”.

[0045] The carbon material used is selected from a group consisting of conductive carbon black, carbon particles, carbon nanoparticles, woven or non-woven carbon cloth, carbon felt, carbon paper, carbon rod, and combination thereof.

[0046] The binder used is selected from a group consisting of PTFE, PVDF, SBR, CMC, PVA.

[0047] The zinc material used is selected from a group consisting of Zinc powder, Zinc Dust, Zinc foil.

[0048] The eutectic electrolyte comprises one or more inorganic transition metal salt(s) of zinc selected from a group consisting of Zinc Chloride, Zinc Acetate, Zinc Methanesulfonate, Zinc Sulphate, Zinc triflate; one or more salt(s) of metal(s) selected from a group consisting of manganese, nickel titanium and copper metal with sulphate anions, methane sulfonate anions, halides anions including chloride, bromide, organic salts of transition metal ions with anions like acetate, oxalates, formates, phosphinates, lactate, malate, citrate, benzoate, ascorbate; one or more Metal hydroxide(s) selected from a group consisting of sodium hydroxide, potassium hydroxide, aluminum hydroxide, zinc hydroxide, calcium hydroxide, cesium hydroxide, magnesium hydroxide, iron hydroxide; wherein one or more inorganic transition metal salt(s) of zinc, one or more salt(s) of metal(s) and one or more Metal hydroxide(s) in molar concentration range 0.1-3:0.1-3:0.05-1 are mixed to a eutectic solvent comprising one or more derivative(s) of methanesulfonic acid selected from its salts with various metal ions selected from group consisting of manganese, zinc, cerium, nickel, titanium, copper, sodium, potassium and calcium; one or more ammonium salt(s) having general formula NH.sub.4X, where X can be selected from a group chloride, methanesulfonate, acetate, sulphate, triflate, trimethanesulfonate; one or more hydrogen bond donor(s) selected from a group consisting of urea, thiourea, glycerol, oxalic acid, acetic acid, ethylene glycol, acetamide, benzamide, adipic acid, benzoic acid, citric acid; wherein the molar ratio of derivative(s) of methane sulfonic acid, ammonium salt(s) and hydrogen bond donor(s) is in the range 0.5-3: 2-7:8-13.

[0049] In order to prepare the eutectic solvent one or more derivative(s) of methanesulfonic acid selected from its salts with various metal ions selected from a group consisting of manganese, zinc, cerium, nickel, titanium, copper, sodium, potassium and calcium; one or more ammonium salt(s) having general formula NH.sub.4X, where X can be selected from a group consisting of chloride, methanesulfonate, acetate, sulphate, triflate, trimethanesulfonate; one or more hydrogen bond donor(s) selected from a group consisting of urea, thiourea, glycerol, oxalic acid, acetic acid, ethylene glycol, acetamide, benzamide, adipic acid, benzoic acid, citric acid; wherein the molar ratio of derivative(s) of methanesulfonic acid, ammonium salt(s) and hydrogen bond donor(s) in the range 0.5-3: 2-7:8-13 are mixed. Upon proper mixing, the mixture starts converting into a liquid eutectic solvent at ambient temperature and pressure. To ensure the proper mixing of the components and to speed up the process, this mixture may be uniformly heated at a temperature up to 60° C. One or more inorganic transition metal salt(s) of zinc selected from a group consisting of Zinc Chloride, Zinc Acetate, Zinc Methanesulfonate, Zinc Sulphate, Zinc triflate; one or more salt(s) of metal(s) selected from a group consisting of manganese, nickel, titanium and copper metal with sulphate anions, methane sulfonate anions, halides anions including chloride, bromide, organic salts of transition metal ions with anions like acetate, oxalates, formates, phosphinates, lactate, malate, citrate, benzoate, ascorbate; one or more Metal hydroxide(s) selected from a group consisting of sodium hydroxide, potassium hydroxide, aluminum hydroxide, zinc hydroxide, calcium hydroxide, cesium hydroxide, magnesium hydroxide, iron hydroxide; wherein one or more inorganic transition metal salt(s) of zinc, one or more salt(s) of metal(s) and one or more Metal hydroxide(s) in molar concentration range 0.1-3:0.1-3:0.05-1 are added to the eutectic solvent and are continuously mixed until they are completely dissolved in the eutectic solvent resulting into eutectic electrolyte.

[0050] For assembling a zinc based rechargeable redox static energy storage device (1) according to the present invention, the cathode (2) pre-infused with eutectic electrolyte and the anode (3) pre-infused with eutectic electrolyte are arranged with a separator between them which allows ion exchange between cathode (2) and anode (3). The cathode (2) is connected with a current collector (5) selected from a group consisting of titanium and carbon material. The anode (2) is connected with a current collector (6) selected from a group consisting of titanium, carbon material, zinc material.

[0051] The thickness ratio of the cathode (2) versus anode (3) ranges between 2-10:1-5.

[0052] The separator (4) used is selected from a group consisting of micro porous PVC, micro porous poly propylene, absorptive glass matt, cellulose filter paper.

[0053] The current collector (5) is selected from a group consisting of titanium and carbon material, wherein carbon material wherein carbon material is selected from the group consisting graphite, woven or non-woven carbon cloth, carbon felt, carbon paper, carbon rod.

[0054] The redox reaction on the cathode side (2) involves manganese ionic species dissolved in the eutectic electrolyte which electro deposits manganese oxide during charging and dissolves back to eutectic electrolyte during discharging.

[0055] The redox reaction on the anode side (3) involves Zinc ionic species dissolved in eutectic electrolyte which electro deposits zinc metal during charging and dissolves back to eutectic electrolyte during discharging.

[0056] The cathode (2) pre-infused with eutectic electrolyte and the anode (3) pre-infused with eutectic electrolyte omits requirement of storing electrolyte in storage tanks and pumping them into the device (1). Further, pre-infusing the electrodes (2, 3) with electrolyte in the device (1) according to the present invention omits the requirement of keeping the device (1) idle, which earlier was a requirement for uniform soaking of electrolyte in electrodes in the existing devices. The high efficiency, long cyclic life, 100% depth of discharge (“DOD”) and high rate charging and discharging capability, simple yet effective and economical design and use of nontoxic and non-corrosive constituents ensures safe and widescale applications of the device according to the present invention.

[0057] In a preferred embodiment according to the present invention, complete device (1) is prepared in the following manner

[0058] Preparation of Eutectic Electrolyte:

[0059] Eutectic electrolyte is prepared by combining 2 moles of calcium methanesulfonate, 5 moles of ammonium chloride, and 10 moles of ethylene glycol in a rotary round-bottom flask at 60 C in an oil bath and rotating it for about 45 minutes obtain a clear, colorless eutectic solvent. Then the eutectic solvent is transferred to a glass bottle. The bottle is placed on a magnetic stirrer plate. 1 mole of Manganese Chloride, 1 mole of Zinc Chloride are then weighed and slowly added to the eutectic solvent under continued stirring. The mixture is stirred until all the salts is dissolved. Then 0.4 Zinc Hydroxide is added to the mixture and is stirred again resulting into slight pinkish transparent eutectic electrolyte. The eutectic electrolyte is then removed from the stirrer plate and stored in a glass bottle.

[0060] Zinc Based Rechargeable Redox Static Energy Storage Device (1) Preparation:

[0061] Carbon material—binder composition is prepared by uniform mixing of conductive acetylene black and a binder solution. In the carbon material—binder composition, the weight ratio of carbon to binder is maintained at 99.1:0.9. Liquid dispersed Polytetrafluoroethylene (PTFE), a non-sticky fluoropolymer, is used as a binder. Diluted Isopropyl alcohol (20 vol %) is used as a solvent for the PTFE, binder. Conductive carbon, AB 50 from Polimaxx, is mixed with the PTFE solution to form a homogeneous clay-like paste in a planetary mixer for 1 hour. Then the clay like paste is laid over the tray and spread across it. This is then followed by vacuum dried at 60° C. for overnight to evaporate the solvent. The carbon material—binder composition is infused with the eutectic electrolyte mentioned above in 1:3 weight ratios. Mixing is done in end mill roll for 30 mins resulting into clay like paste. The paste is thereafter used to prepare sheets of controlled thickness by repeatedly rolling using TOB-SG-100L lab roll press machine. For the cathode (2) thickness of sheet is maintained at 1 mm and for the anode (3) the thickness is 0.5 mm A thin zinc foil having a thickness of 30 microns is placed over sheet of thickness 0.5 mm forming anode. Individual titanium foil is connected to each of the electrodes (2, 3) and served as a current collector for both electrodes (2, 3).

[0062] The electrodes (2, 3) with current collectors are assembled with Celgard 3501, a polypropylene-based microporous membrane, used as the separator (4) between them.

[0063] The resultant embodiment is termed as “Test device (1)”

[0064] FIG. 1 is exploded view of preferred embodiment that is termed as “test device (1)”

EXPERIMENTATION

[0065] Testing:

[0066] Test device (1) is prepared as above and tested using cyclic voltammetry (CV) on a Biologic VPM3 electrochemical workstation at a scanning rate of 5 mV s-1.

[0067] Constant Current Charge and Constant Current Discharge procedures are used to test the test device (1). The test device (1) is also tested at different C rate of C/7, C/4, 1C, 5C.

[0068] The test device (1) is tested at voltages ranging from 0.5 to 1.9 volts. The test device (1) is tested using a Neware battery cycler. When the test device (1) is charged, soluble Manganese ions in the eutectic electrolyte diffuse to the cathode and deposit on the various forms of conductive carbon black as solid Manganese oxide, while Zinc ions are electrodeposited on the carbon side of anode. The homogeneous layer of as-deposited Manganese oxide on the cathode is dissolved back to soluble Manganese ions in the eutectic electrolyte during battery discharge, and the as-deposited Zinc on the anode is dissolved back to Zinc ions in the eutectic electrolyte.

[0069] Experiment 1

[0070] Test device (1)'s cyclic voltammograms is obtained to determine reversibility and stability as a possible use case for Zinc redox batteries. Test device (1) CVs of a device from 1 V to 2.2 V at a scan rate of 5 mV/s for 1000 cycles. These results reveal that the eutectic electrolyte has a mainly faradaic reaction and are compatible with galvanic charge discharge patterns.

[0071] The above approach is used to prepare test device (1), which are then tested utilizing constant current procedures.

[0072] For Manganese Oxide deposition and dissolution, the CV curve of the test device (1) shows a comparable oxidation and reduction peak. At a potential range of 0.9-2.2 V, a pair of well-defined peaks can be seen. The electrochemical deposition of Manganese Oxide from the soluble eutectic electrolyte is assigned to the oxidation peak at 1.7V, whereas the dissolution of Manganese Oxide to Mn.sup.2+ Ions is attributed to the reduction peak at 1.35V. The oxidation-to-reduction ratio is 1, indicating that the process is highly reversible.

[0073] FIG. 2 shows a scan rate of 5 mV/s, the cyclic voltammetry curve of a test-device zinc-based redox battery. At a possible range of 1-2.2V, a pair of well-defined peaks could be seen. The ratio of oxidation and reduction is ˜1 indicating highly reversible reaction.

[0074] Experiment 2

[0075] To determine the crystalline structure of the electrodes at 0% state of charge and at 100% state of charge (SOC) is identified by Xray diffraction (XRD, PANalytical) with Cu Kα radiation.

[0076] Two identical test devices A and B are prepared using the above method and both are fully charged.

[0077] Cathode of test device A is removed from device and is separately tested which is considered as 100% SOC.

[0078] Test device B is fully discharged at a constant current rate and Cathode is removed from test device B and is separately tested which is considered as 0% SOC.

[0079] At 100% SOC, the oxidation product is further confirmed by X-ray diffraction (XRD), which demonstrated a type of beta, gamma Manganese Oxide with the birnessite structure and belong to the hexagonal crystal system. After discharging to 0% SOC state, the pattern of Manganese Oxide cannot be observed which further confirm the dissolution of Manganese Oxide.

[0080] FIG. 3 shows XRD pattern of cathode of both test devices A and B at 100% and 0%, respectively, state of charge after removing carbon peaks. At 0% SOC there are no obvious peaks except for titanium current collector peaks while at 100% SOC there are Manganese Dioxide peaks.

[0081] Experiment 3

[0082] To determine Zinc Redox battery performance of a test device (1).

[0083] Test device (1) is prepared using the above method and tested using constant current charge and discharge techniques as described above.

[0084] Within the range of 0.5 to 1.9V, charge/discharge curves reveal a highly reversible electrochemical process. Low polarization is shown by the average charge and discharge voltage plateaus of 1.55 V and 1.4 V, respectively. The coulombic efficiency and energy efficiency of a highly reversible electrochemical reaction are both approximately >99% and >90%, respectively. FIG. 4 shows Galvanostatic charge-discharge profile of device. Two voltage plateaus at around 1.5 V and 1.4 V represents charging and discharging process, respectively.

[0085] Experiment 4

[0086] To determine the effect of constant cycling at lower C rate of C/5.

[0087] Test device (1) is prepared using the above method and tested using constant current techniques as described above.

[0088] Test device (1) is tested by cycling under a voltage limit of 0.5 to 1.9 V to investigate the cycling stability at slow C rate of C/5. It shows that the capacity improves after each full cycle for the first 15 cycles. This indicates there is a more electrolyte utilization over prolonged cycling period. FIG. 5 shows cycling of a test device (1) at a constant current, the device's charge-discharge behavior. Both profiles show a steady increase in discharge capacity as the cycle life increases.

[0089] Experiment 5

[0090] To determine the effect of constant voltage charging on the Zinc Redox battery test device (1).

[0091] Test device (1) is prepared using the above method and tested using constant current techniques as described above.

[0092] During charging at a constant voltage of 1.7 V, soluble Mn.sup.2+ ions in the eutectic electrolyte is oxidized to Manganese Oxide deposited evenly on the carbon substrate, while simultaneous electrodeposition of Zn occurs on the anode. The voltage value of 1.7 V ensures both a successful electrodeposition reaction and the suppression of any other side reaction. Even with constant voltage charging methods the test device (1) is stable and has higher efficiency of 80%. FIG. 6 shows Galvanostatic charge-discharge profile of test device (1) at constant voltage 1.7 V charge—constant current discharge (CV-CC) condition.

[0093] Experiment 6

[0094] To determine the effect of C rating on Zinc Redox battery test device (1).

[0095] Test device (1) is prepared using the above method and tested using constant current charge and discharge techniques as described above.

[0096] Test device (1) is tested by cycling under a different C rating with voltage limit of 0.5 to 1.9V to investigate stability of test device (1) under higher load. Even at higher C rate of 5C it shows high energy efficiency of 82% indicating lower internal resistance of the test device (1).

[0097] FIG. 7 shows Galvanostatic charge-discharge profile of device at different current rate, i.e., C/7, C/4, 1C, 5C. High columbic efficiency and low polarization is observed throughout the current range.

[0098] Experiment 7

[0099] To determine the effect of temperature on Zinc Redox battery test device (1) capacity.

[0100] Test device (1) is prepared using the above method and tested using constant current charge and discharge techniques as described above.

[0101] Test device (1) is tested by cycling under a different temperature rating of 15° C. and 30° C. It is observed that at higher temperature the capacity increases as compared to lower temperature. FIG. 8 shows the cycle performance—Coulombic efficiency and discharge capacity of prepared device in different temperature of 15° C. (Lower Dot) and 30° C. (Upper Dot).

[0102] Experiment 8

[0103] To determine the effect of prolong cycling at different C rates.

[0104] Test device (1) is prepared using the above method and tested using constant current techniques as described above.

[0105] The device shows good cycling stability at 3C showing 95% capacity retentions even after 1300 cycles. The device with a higher rate capability of 5C shows a stable cycle life up to 3500 cycles. FIG. 9 shows Cycle life, Coulombic efficiency of the Zinc Redox battery at 3C rate. The Zinc Redox battery exhibits excellent cycling stability. Close to 95% of the maximum discharge capacity is maintained after prolong cycling. The Zinc Redox battery exhibits excellent cycling stability, even at high rates. FIG. 10 shows Cycle life, Coulombic efficiency of the Zinc Redox battery at 5C rate. The Zinc Redox battery exhibits excellent cycling stability, even at high rates.

[0106] Changes and modifications in the specifically-described embodiments may be carried out without departing from the principles of the present invention, which is intended to be limited only by the scope of the appended claims as interpreted according to the principles of patent law including the doctrine of equivalents.