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METHOD FOR PRODUCTION BY AQUEOUS ROUTE OF A ZINC ELECTRODE

20200203716 · 2020-06-25

    Inventors

    Cpc classification

    International classification

    Abstract

    Disclosed is a production method for a zinc electrode with in situ formation of calcium zincate crystals. The method includes notably the steps of preparation of a mixture, growth of crystals, slowing of the growth and production of the electrode.

    Claims

    1-12. (canceled)

    13. A method for producing a zinc electrode, comprising at least: preparing a mixture comprising zinc oxide ZnO and/or at least one precursor of ZnO thereof, calcium hydroxide Ca(OH).sub.2 and water H.sub.2O, where a molar ratio defined by ZnO/Ca(OH).sub.2 is included between 2/1 and 10/1, ripening said mixture, so as to form calcium zincate crystals Ca(OH).sub.2.2Zn(OH).sub.2.2H.sub.2O according to a reaction defined in equation 5
    2ZnO+Ca(OH).sub.2+4H.sub.2O.fwdarw.Ca(OH).sub.2.2Zn(OH).sub.2.2H.sub.2O, Equation 5 adding solvent to the ripened mixture so as to interrupt the ripening by slowing the growth of the calcium zincate crystals Ca(OH).sub.2.2Zn(OH).sub.2.2H.sub.2O, and producing a zinc electrode with said mixture comprising calcium zincate crystals Ca(OH).sub.2.2Zn(OH).sub.2.2H.sub.2O.

    14. The method according to claim 13, wherein said ripening is performed at ambient temperature between 20 and 35 C.

    15. The method according to claim 13, wherein the ripening is executed for a time included between 3 minutes and 20 minutes.

    16. The method according to claim 13, wherein the added solvent is an alcohol.

    17. The method according to claim 13, wherein said calcium zincate crystals have an average size by number included between 10 and 200 m.

    18. The method according to claim 13, wherein producing the zinc electrode comprises at least: passing the mixture comprising calcium zincate crystals Ca(OH).sub.2.2Zn(OH).sub.2.2H.sub.2O in a calender; pressing the passed mixture; drying the pressed mixture.

    19. The method according to claim 13, wherein a binder is added.

    20. The method according to claim 19, wherein the binder is polytetrafluoroethylene.

    21. The method according to claim 13, wherein an additive is added and said additive is selected from bismuth oxide, mercury oxide, indium hydroxide or an arbitrary electronic conductor, and a mixture thereof.

    22. The method according to claim 13, wherein said molar ratio defined by ZnO/Ca(OH).sub.2 is included between 3/1 and 6/1.

    23. A zinc electrode obtained by the method according to claim 13.

    24. A zinc-air battery comprising at least one zinc electrode according to claim 23 as a negative electrode.

    25. The method according to claim 14, wherein the ripening is executed for a time included between 3 minutes and 20 minutes.

    26. The method according to claim 14, wherein the added solvent is an alcohol.

    27. The method according to claim 15, wherein the added solvent is an alcohol.

    28. The method according to claim 14, wherein said calcium zincate crystals have an average size by number included between 10 and 200 m.

    29. The method according to claim 15, wherein said calcium zincate crystals have an average size by number included between 10 and 200 m.

    30. The method according to claim 16, wherein said calcium zincate crystals have an average size by number included between 10 and 200 m.

    31. The method according to claim 14, wherein producing the zinc electrode comprises at least: passing the mixture comprising calcium zincate crystals Ca(OH).sub.2.2Zn(OH).sub.2.2H.sub.2O in a calender; pressing the passed mixture; drying the pressed mixture.

    32. The method according to claim 15, wherein producing the zinc electrode comprises at least: passing the mixture comprising calcium zincate crystals Ca(OH).sub.2.2Zn(OH).sub.2.2H.sub.2O in a calender; pressing the passed mixture; drying the pressed mixture.

    Description

    BRIEF DESCRIPTION OF THE DRAWINGS

    [0098] FIG. 1 shows an illustration of the calcium zincate crystals Ca(OH).sub.2.2Zn(OH).sub.2.2H.sub.2O (1) formed during step b according to the method of the present invention. Said crystals are formed in situ in the mixture of zinc oxide (ZnO), calcium hydroxide (Ca(OH).sub.2) and water (H.sub.2O)(2).

    EXAMPLES

    [0099] A zinc electrode was prepared by means of the method according to the invention.

    [0100] In the case from the present example, the quantities of reagents presented in Table 1 were used.

    TABLE-US-00001 TABLE 1 Reagent Quantity ZnO 150 g Ca(OH).sub.2 30 g Deionized water 30 mL PTFE 20 mL Ethanol 30 mL

    [0101] The zinc oxide powder (Merck Emsure) is mechanically mixed with calcium hydroxide (Merck) in a mixer for 5 minutes at 23 C. While keeping the mixer running, deionized water is added to the mixture at constant speed over about 30 seconds, while providing a good homogeneity of the mixture. The addition of water seeds the formation of calcium zincate crystals.

    [0102] The mixture is held under stirring for 3 minutes. Then, an aqueous suspension of PTFE with a 60% concentration (Aldrich) is added over 1 minute.

    [0103] The mixture is again kept under stirring for 5 minutes during which the calcium zincate crystals continue to form and grow.

    [0104] The ripening reaction is interrupted by addition of ethanol over 10 seconds.

    [0105] The resulting mixture is then passed in a calender, pressed and dried in order to form a zinc electrode in the discharged state.