WO2021133263A1

WO2021133263A1 - Rechargeable aqueous zinc-iodine cell

Info

Publication number: WO2021133263A1
Application number: PCT/TH2019/000070
Authority: WO
Inventors: Soorathep KHEAWHOM; Wathanyu KAO-IAN
Original assignee: Chulalongkorn University
Priority date: 2019-12-23
Filing date: 2019-12-23
Publication date: 2021-07-01

Abstract

The present invention discloses a rechargeable aqueous zinc -iodine cell and a method of manufacturing the zinc-iodine cell. The zinc-iodine cell comprises a negative electrode comprising zinc foil or zinc powder mixed with carbon and a binder; a positive electrode comprising iodine adsorbed on activated carbon and mixed with carbon black and an anionic- polyelectrolyte binder of a polymer containing sulfonyl group or carboxyl group; a current collector of the positive electrode selected from the group consisting of graphite sheet, graphite felt and carbon cloth; a porous exchange membrane separator, and a mild acidic aqueous electrolyte solution comprising zinc sulphate or organic zinc sulphate with or without additives.

Description

RECHARGEABLE AQUEOUS ZINC-IODINE CELL BACKGROUND OF THE INVENTION A. Technical field

[1] The present invention generally relates to a rechargeable aqueous metal -halogen cell. B. Description of related art

[2] A substantial amount of interest has recently been centred on the development of high energy density, electrochemically rechargeable, energy storage systems due to exhaustion of fuel oil. The aqueous zinc-iodine battery is one of the most promising rechargeable battery systems. Aqueous zinc-iodine battery, which is based on the reversible conversion reaction Zn + h < Zn²⁺ + 2G, has many attractive features such as high energy density, high safety, eco-friendly, and low cost. Zinc is an ideal negative electrode due to its low cost, high volumetric energy density (5,888 mAh cm ³), and excellent stability. Iodine is an attractive cathode material with high energy density. Nonetheless, iodine suffers from several issues, such as weak electrical conductivity and easy sublimation at room temperature.

[3] Besides, owing to the insoluble nature ofh in an aqueous electrolyte, the battery is constrained by a limited energy density. To improve the energy density, iodine can be infused into a porous activated carbon by sublimation of h, which significantly enhances battery performance (Bai et al., Nano Research 2018, 11(7): 3548). Alternatively, iodine is adsorbed on a carbon cathode by simply soaking carbon cloth in an iodine/water mixture (Li et al., Chemical Communications 2018, 54: 6792). Though confining iodine species in porous carbon can improve iodine loading and utilization, low cyclability and high charging overpotential remain unsolved. The high solubility of the discharged products (G) in an aqueous electrolyte contributes to these issues. Few patent references that attempt to solve the aforementioned problems are disclosed as follows.

[4] CN107666015B entitled “water-phase electrolyte system zinc iodine secondary battery and preparation method thereof’ discloses a battery comprising a positive electrode, a negative electrode, a water-phase electrolyte and a diaphragm. The positive electrode is a composition material containing iodine, the negative electrode is pure zinc or zinc base alloy, and the water-phase electrolyte is a zinc saltwater solution. When the battery works, reversible chemical reaction between zinc and iodine is carried out, so that the battery is essentially different from a zinc ion battery on the basis of reversibly embedding or separating a zinc ion in/from a positive electrode material.

[5] JP2019053869 entitled “Secondary battery, electrolyte for the same, and method for producing the same” discloses a secondary battery including: a hydrophilic ion liquid; and an electrolytic solution containing water, a negative electrode active material containing at least one of a metal and an ion of the metal, and a positive electrode active material containing at least one of iodine and an iodine ion.

[6] However, the above patent references lack to provide an efficient energy storage system to decrease the polarization of the battery during charging process to trap discharged products at the positive electrode, and hence it is desired to develop an energy storage system or battery to address the afore discussed issues.

SUMMARY OF THE INVENTION

[7] The present invention discloses a rechargeable aqueous zinc-iodine cell and a method of manufacturing the zinc-iodine cell.

[8] The zinc-iodine cell comprises a negative electrode comprising zinc mixed with carbon and a binder; a positive electrode comprising iodine adsorbed on activated carbon and mixed with carbon black and an anionic-polyelectrolyte binder of a polymer containing sulfonyl group or carboxyl group; a current collector of the positive electrode selected from the group consisting of graphite sheet, graphite felt and carbon cloth; a porous exchange membrane separator, and a mild acidic aqueous electrolyte solution comprising zinc sulphate or organic zinc sulphate with or without additives.

[9] In another embodiment, a method of fabricating battery with carboxymethyl cellulose (CMC) binder is disclosed. At one step, an aqueous iodine solution of iodine and potassium iodide dissolved in deionized water is provided. At another step, activated carbon is added to the iodine solution to obtain a mixture. At another step, the mixture is filtered to obtain a solid. Further, the solid is washed with deionized water. At another step, the solid is mixed with a polymer containing sulfonyl group or carboxyl group, conductive carbon and deionized water, and the mixture is stirred to obtain a slurry. At another step, a graphite sheet is coated with the slurry and allowed to dry naturally at room temperature.

[10] In one embodiment, a method for fabricating battery with carboxymethyl cellulose (CMC) coating is disclosed. At step (a), the activated carbon is mixed with a polymer that has no sulfonyl group or carboxyl group, conductive carbon and deionized water. Then the mixture is stirred to obtain a slurry. At step (b), a graphite sheet is coated with the slurry and allowed to dry naturally at room temperature. At step (c), the coated graphite sheet obtained in (b) is soaked in an aqueous iodine solution of iodine and potassium iodide dissolved in deionized water for 24 hours. At step (d), the coated graphite sheet obtained in (b) is soaked in an aqueous solution of the polymer containing sulfonyl group or carboxyl group for 24 hours. At step (e), the coated graphite sheet is allowed to dry naturally at room temperature.

[11] Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating specific embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF DRAWINGS

[12] FIG. 1 exemplarily illustrates a method of manufacturing a rechargeable aqueous zinc-iodine cell, according to an embodiment of the present invention.

[13] FIG. 2 exemplarily illustrates a method of manufacturing the rechargeable aqueous zinc-iodine cell, according to another embodiment of the present invention. [14] FIG. 3 is a graph illustrating capacity retention of a battery fabricated without Carboxymethyl cellulose (CMC) binder, according to a conventional method.

[15] FIG. 4 is a graph illustrating round-trip efficiency of a battery with CMC coating, according to an embodiment of the present invention.

[16] FIG. 5 is a graph illustrating the relative capacity of a battery with CMC binder, according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[17] A description of embodiments of the present invention will now be given with reference to the figures. It is expected that the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

[18] The present invention discloses a rechargeable aqueous zinc-iodine cell and a method of manufacturing the zinc-iodine cell. The present invention addresses the issues of high solubility of discharged products (G) in an aqueous electrolyte, by trapping the discharged products at the positive electrode.

[19] Accordingly, G is encapsulated on positive active material using an anionic polyelectrolyte containing carboxyl or sulfonyl groups, such as sodium carboxymethyl cellulose. It is known that an anionic polyelectrolyte can dissolve in an aqueous electrolyte. However, according to the present invention, in a mild acidic electrolyte, e.g., zinc sulfate or organic zinc sulphate, an anionic polyelectrolyte shows excellent stability and could also be employed as a binder. [20] The present invention further discloses a rechargeable aqueous zinc-iodine battery and a method of manufacturing the zinc-iodine battery. The rechargeable aqueous zinc-iodine battery comprises a negative electrode, a positive electrode, a separator for separating the cathode from the anode and an aqueous or gel electrolyte.

[21] In one embodiment, the positive electrode is composed of a current collector. In one embodiment, the negative electrode comprising zinc foil or zinc powder mixed with carbon and a binder; the positive electrode comprising iodine adsorbed on activated carbon and mixed with carbon black and an anionic-polyelectrolyte binder of a polymer containing sulfonyl group or carboxyl group; and the current collector of the positive electrode selected from the group consisting of graphite sheet, graphite felt and carbon cloth. In one embodiment, the separator is a porous membrane separator, and the electrolyte is a mild acidic aqueous electrolyte solution comprising zinc sulphate (ZnSCL) or organic zinc sulphate such as Zn (CF₃SC>₃)₂. In one embodiment, the electrolyte solution comprises Zn (TFSI)₂ or K₂SO₄. In another embodiment, the electrolyte solution comprises zinc sulphate (ZnSCfi) or organic zinc sulphate with one or more additives such as sodium sulphate (Na₂SC>₄). The additives improve the performance of the battery. In another embodiment, the electrolyte solution comprises zinc sulphate (ZnSCfi) or organic zinc sulphate without additives. In one embodiment, the thickness of the separator could be adjusted. In another embodiment, the thickness is chosen between 0.2 to 0.01 mm

[22] In one embodiment, the battery could be fabricated in different form factors such as coin cell, pouch cell, cylindrical cell or prismatic cell, similar to Li-ion battery cell.

[23] Referring to FIG. 1, a method 100 for manufacturing a rechargeable aqueous metal- halogen cell, particularly, zinc-iodine cell is disclosed. At step 102, an aqueous iodine solution of iodine and potassium iodide dissolved in deionized water is provided. At step 104, activated carbon is added to the iodine solution to obtain a mixture. At step 106, the mixture is filtered to obtain a solid. Further, the solid is washed with deionized water. At step 108, the solid is mixed with a polymer containing sulfonyl group or carboxyl group, conductive carbon and deionized water, and the mixture is stirred to obtain a slurry. At step 110, a graphite sheet is coated with the slurry and allowed to dry naturally at room temperature. [24] Referring to FIG. 2, a method 200 for manufacturing a rechargeable aqueous metal- halogen cell is disclosed. At step 202, the activated carbon is mixed with a polymer that has no sulfonyl group or carboxyl group, conductive carbon and deionized water. Then the mixture is stirred to obtain a slurry. At step 204, a graphite sheet is coated with the slurry and allowed to dry naturally at room temperature. At step 206, the coated graphite sheet obtained in step 204 is soaked in an aqueous iodine solution of iodine and potassium iodide dissolved in deionized water for 24 hours. At step 208, the coated graphite sheet obtained in step 204 is soaked in an aqueous solution of the polymer containing sulfonyl group or carboxyl group for 24 hours. At step 210, the coated graphite sheet is allowed to dry naturally at room temperature.

[25] Referring to FIG. 3, a graph 300 illustrating capacity retention of a battery fabricated without CMC binder, according to a conventional method.

[26] In one embodiment, a method for fabricating battery with CMC coating is disclosed, which involves depositing the active materials using non-polyelectrolyte binder and coating polyelectrolyte at the final stage. At step (a), the activated carbon is mixed with a polymer that has no sulfonyl group or carboxyl group, conductive carbon and deionized water. Then the mixture is stirred to obtain a slurry. At step (b), a graphite sheet is coated with the slurry and allowed to dry naturally at room temperature. At step (c), the coated graphite sheet obtained in (b) is soaked in an aqueous iodine solution of iodine and potassium iodide dissolved in deionized water for 24 hours. At step (d), the coated graphite sheet obtained in (b) is soaked in an aqueous solution of the polymer containing sulfonyl group or carboxyl group for 24 hours. At step (e), the coated graphite sheet is allowed to dry naturally at room temperature. Referring to FIG. 4, the batteries fabricated by this method of the present invention exhibit significant improvement at high current density. The benefit of the present invention is confirmed with round-trip efficiency. In particular, the CMC-binder shows the round-trip efficiency above 90% of graph 400 of FIG. 4.

[27] In another embodiment, a method of fabricating battery with CMC binder is disclosed, which involves depositing the active materials using polyelectrolyte binder. At one step, an aqueous iodine solution of iodine and potassium iodide dissolved in deionized water is provided. At another step, activated carbon is added to the iodine solution to obtain a mixture. At another step, the mixture is filtered to obtain a solid. Further, the solid is washed with deionized water. At another step, the solid is mixed with a polymer containing sulfonyl group or carboxyl group, conductive carbon and deionized water, and the mixture is stirred to obtain a slurry. At another step, a graphite sheet is coated with the slurry and allowed to dry naturally at room temperature. FIG. 5 is a graph 500 illustrating relative capacity of a battery with CMC binder, according to an embodiment of the present invention. The result of voltage profiles also confirms that the present invention benefits significantly enhancing the discharge voltage and also capacity of the battery especially at high current densities.

[28] The foregoing description comprise illustrative embodiments of the present invention. Having thus described exemplary embodiments of the present invention, it should be noted by those skilled in the art that the within disclosures are exemplary only, and that various other alternatives, adaptations, and modifications may be made within the scope of the present invention. Merely listing or numbering the steps of a method in a certain order does not constitute any limitation on the order of the steps of that method. Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions. Although specific terms may be employed herein, they are used only in generic and descriptive sense and not for purposes of limitation. Accordingly, the present invention is not limited to the specific embodiments illustrated herein. While the above is a complete description of the preferred embodiments of the invention, various alternatives, modifications, and equivalents may be used. Therefore, the above description and the examples should not be taken as limiting the scope of the invention, which is defined by the appended claims.

Claims

1. A rechargeable aqueous zinc-iodine battery comprising: a negative electrode comprising zinc mixed with carbon and a binder; a positive electrode comprising iodine adsorbed on activated carbon and mixed with carbon black and an anionic-polyelectrolyte binder of a polymer containing sulfonyl group or carboxyl group; a current collector of the positive electrode; a porous exchange membrane separator, and a mild acidic aqueous electrolyte solution comprising at least one of zinc sulphate or organic zinc sulphate.

2. The battery of claim 1, wherein the separator comprises thickness between 0.2 to 0.01 mm

3. The battery of claim 2, wherein the thickness of the separator is variable.

4. The battery of claim 1 , wherein the current collector is selected from the group consisting of graphite sheet, graphite felt and carbon cloth.

5. The battery of claim 1, is adapted to be fabricated in different form factors.

6. The battery of claim 1 , is fabricated in one or more forms selected from the group consisting of coin cell, pouch cell, cylindrical cell and prismatic cell.

7. The battery of claim 1 , wherein the mild acidic aqueous electrolyte solution comprises at least one of zinc sulphate or organic zinc sulphate with or without one or more additives.

8. A method for manufacturing a rechargeable aqueous metal-halogen cell comprising the steps of: a) providing an aqueous iodine solution of iodine and potassium iodide dissolved in deionized water; b) adding activated carbon to the iodine solution to obtain a mixture; c) filtering the mixture and washing the filtered solid with deionized water; d) mixing the solid with a polymer containing sulfonyl group or carboxyl group, e) conductive carbon and deionized water, and stirring the mixture to obtain a slurry, and f) coating a graphite sheet with the slurry and allowing the coated graphite sheet to dry naturally at room temperature.

9. The method of claim 8, wherein the cell is fabricated in one or more forms selected from the group consisting of coin cell, pouch cell, cylindrical cell and prismatic cell.

10. A method for manufacturing a rechargeable aqueous metal-halogen cell comprising the steps of: a) mixing activated carbon with a polymer that has no sulfonyl group or carboxyl group, conductive carbon and deionized water, and stirring the mixture to obtain a slurry; b) coating a graphite sheet with the slurry and allowing the coated graphite sheet to dry naturally at room temperature; c) soaking the coated graphite sheet obtained in (b) in an aqueous iodine solution of iodine and potassium iodide dissolved in deionized water for 24 hours; d) soaking the coated graphite sheet obtained in (b) in an aqueous solution of the polymer containing sulfonyl group or carboxyl group for 24 hours, and e) allowing the coated graphite sheet to dry naturally at room temperature.

11. The method of claim 10, wherein the cell is fabricated in one or more forms selected from the group consisting of coin cell, pouch cell, cylindrical cell and prismatic cell.