High voltage rechargeable Zn-MnO2 battery

Abstract

The invention discloses a high voltage rechargeable Zn—MnO.sub.2 battery. The structure of the Zn—MnO.sub.2 battery includes zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode. The ion exchange membrane comprises a cation exchange membrane, an anion exchange membrane or a proton exchange membrane. According to the invention, by using a composite electrolyte system (alkaline electrolyte/ion exchange membrane/acid electrolyte), a high voltage rechargeable Zn—MnO.sub.2 battery is obtained. According to the invention, an open circuit voltage of up to 2.7V is obtained, greatly improving the discharge voltage, and at the same time increasing the discharge capacity and enabling cyclic charge and discharge. The invention is of great importance in science research, beneficial to society and economics.

Claims

1. A high voltage rechargeable Zn—MnO.sub.2 battery, wherein a structure of the Zn—MnO.sub.2 battery comprises zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode.

2. The high voltage rechargeable Zn—MnO.sub.2 battery according to claim 1, wherein the zinc electrode is prepared by using a zinc foil, a zinc paste or zinc powder.

3. The high voltage rechargeable Zn—MnO.sub.2 battery according to claim 1, wherein the alkaline electrolyte comprises an alkaline liquid electrolyte, an alkaline solid electrolyte, an alkaline polymer electrolyte or an alkaline gel electrolyte.

4. The high voltage rechargeable Zn—MnO.sub.2 battery according to claim 3, wherein the alkaline liquid electrolyte comprises a potassium hydroxide solution, a lithium hydroxide solution or a sodium hydroxide solution with or without an additive, and the additive comprises zinc chloride, zinc sulfate, zinc nitrate, zinc acetate or zinc oxide.

5. The high voltage rechargeable Zn—MnO.sub.2 battery according to claim 3, wherein the electrolyte in the alkaline gel electrolyte is one or more of potassium hydroxide, sodium hydroxide and lithium hydroxide, and a gel skeleton is one or a mixture of two or more of polyvinyl alcohol, polyacrylic acid, potassium polyacrylate, and polyethylene oxide.

6. The high voltage rechargeable Zn—MnO.sub.2 battery of claim 1, wherein said ion exchange membrane comprises a cation exchange membrane, an anion exchange membrane or a proton exchange membrane.

7. The high voltage rechargeable Zn—MnO.sub.2 battery according to claim 1, wherein the acid electrolyte comprises an acidic liquid electrolyte, an acidic solid electrolyte, an acidic polymer electrolyte or an acidic gel electrolyte.

8. The high voltage rechargeable Zn—MnO.sub.2 battery according to claim 7, wherein the acidic liquid electrolyte comprises a sulfuric acid solution, a phosphoric acid solution, a hydrochloric acid solution or a nitric acid solution with or without an additive, and the additive comprises manganese sulfate, manganese nitrate, manganese chloride, manganese acetate.

9. The high voltage rechargeable Zn—MnO.sub.2 battery according to claim 7, wherein the acidic gel electrolyte comprises a polyvinyl alcohol-sulfate electrolyte or a polyvinyl alcohol-phosphoric acid electrolyte.

10. The high voltage rechargeable Zn—MnO.sub.2 battery according to claim 1, wherein the MnO.sub.2 electrode comprises a MnO.sub.2 powder electrode or an electrodeposited MnO.sub.2 electrode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings illustrate one or more embodiments of the present invention and, together with the written description, serve to explain the principles of the invention. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment.

[0044] Other features, objects, and advantages of the present invention will become apparent from the detailed description of the non-limiting embodiments with reference to accompanying drawings.

[0045] FIG. 1 is a schematic structural view of a high voltage rechargeable Zn—MnO.sub.2 battery of the present invention;

[0046] FIG. 2 is a schematic view showing a discharge curve of a high voltage rechargeable Zn—MnO.sub.2 battery VS that of a conventional alkaline Zn—MnO.sub.2 battery of the fourth embodiment;

[0047] FIG. 3 is a charging and discharging curve of a high voltage rechargeable Zn—MnO.sub.2 battery of the fourth embodiment;

[0048] Among them, 1 refers to a MnO.sub.2 electrode, 2 refers to an acid electrolyte, 3 refers to an ion exchange membrane, 4 refers to an alkaline electrolyte, and 5 refers to a zinc electrode.

DETAILED DESCRIPTION

[0049] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the present invention are shown. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure is thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.

[0050] Embodiments of the invention are illustrated in detail hereinafter with reference to accompanying drawings. It should be understood that specific embodiments described herein are merely intended to explain the invention, but not intended to limit the invention.

[0051] The invention will now be described in detail in conjunction with the specific embodiments and drawings. The following embodiments are intended to facilitate understanding of the invention by those skilled in the art, but are not intended to limit the invention in any way. It should be noted that a number of variations and modifications may be made by those skilled in the art without departing from the inventive concept, which are all within the scope of protection of the present invention.

[0052] The high voltage rechargeable Zn—MnO.sub.2 battery of the invention has the structure of the zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode. The specific preparation steps are as follows.

[0053] 1. Preparation of the zinc electrode, in which a zinc foil or a zinc paste can be used directly.

[0054] 2. Preparation of the alkaline electrolyte, in which an alkaline electrolyte or an alkaline gel electrolyte can be used directly.

[0055] The alkaline electrolyte includes, but is not limited to, a potassium hydroxide solution, a lithium hydroxide solution or a sodium hydroxide solution with or without an additive, in which the alkali metal hydroxide solution has a concentration of 10 g/L to 1000 g/L. The additive includes, but is not limited to, zinc chloride, zinc sulfate, zinc nitrate, zinc acetate, zinc oxide, and the like.

[0056] The electrolyte in the alkaline gel electrolyte is one or more of potassium hydroxide, sodium hydroxide, and lithium hydroxide. The gel matrix is one or a mixture of at least two of polyvinyl alcohol, polyacrylic acid, potassium polyacrylate, polyethylene oxide. The electrolyte is added to the alkaline gel electrolyte as a raw material in the form of a solution.

[0057] 3. Ion exchange membrane: including but not limited to the following: cation exchange membrane, anion exchange membrane, proton exchange membrane.

[0058] 4. Preparation of the acid electrolyte, in which an acid electrolyte or an acidic gel electrolyte can be used directly.

[0059] The acid electrolyte includes, but is not limiting to, sulfuric acid solution, phosphoric acid solution, hydrochloric acid solution, nitric acid solution, and the like with or without an additive, where the acid concentration is from 5 g/L to 1000 g/L. Such additive includes, but is not limited to, manganese sulfate, manganese nitrate, manganese chloride, manganese acetate, and the like.

[0060] The acidic gel electrolyte includes, but is not limited to, the following: polyvinyl alcohol-sulfuric acid (PVA-H.sub.2SO.sub.4) electrolyte, polyvinyl alcohol-phosphoric acid (PVA-H.sub.3PO.sub.4) electrolyte.

[0061] 5. MnO.sub.2 electrode, in which the MnO.sub.2 powder is mixed with a conductive agent and an additive.

[0062] For specific details, please refer to the following embodiments.

Embodiment 1

[0063] The embodiment relates to a high voltage rechargeable Zn—MnO.sub.2 battery, which has a structure of zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode. The specific preparation steps are as follows.

[0064] 1) Preparation of the zinc electrode, in which a zinc plate is taken as the zinc electrode.

[0065] 2) Preparation of the alkaline electrolyte, in which 3 g of polyvinyl alcohol is heated and dissolved in 24 mL of water, to form a uniform and stable solution, and then the solution is poured into 6 mL of 500 g/L potassium hydroxide solution+200 g/L zinc acetate solution. After stirring evenly, the resulted solution is placed in a freezer. Subsequently, the solution is taken out to melt for use, resulting in an alkaline gel electrolyte of polyvinyl alcohol-potassium hydroxide-zinc acetate, in which the potassium hydroxide concentration in the liquid portion is 100 g/L, and the zinc acetate concentration is 40 g/L.

[0066] 3) Ion exchange membrane, in which the ion exchange membrane of the high-voltage Zn—MnO.sub.2 battery system of the present embodiment may be a proton exchange membrane, an anion exchange membrane, a cation exchange membrane or the like. Specifically, in the present embodiment, a sulfonic acid-based cation exchange membrane is used.

[0067] 4) Preparation of the acid electrolyte, in which 3 g of polyvinyl alcohol is heated and dissolved in 24 mL of water to form a uniform and stable solution, and then 6 mL of 500 g/L sulfuric acid solution is poured thereinto. After stirring evenly, the resulted solution is placed in a freezer. Then it is taken out to melt for use, resulting in a polyvinyl alcohol-sulfate acid gel electrolyte having a sulfuric acid concentration of 100 g/L in the liquid portion.

[0068] 5) Preparation of the MnO.sub.2 electrode, in which 8 g of MnO.sub.2 powder is uniformly mixed with 1 g of graphite powder and 1 g of polyvinylidene fluoride, and the obtained mixture is added to 0.4 g of a 100 g/L sulfuric acid solution, stirred, and dried to serve as a MnO.sub.2 electrode.

[0069] 6) Battery assembly, in which the battery is formed with a structure of the zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode in combination. Its schematic structure is shown in FIG. 1.

[0070] The resulted battery has an open circuit voltage above 2.6V, and a working platform voltage above 2.5V. The resulted battery is chargeable and dischargeable, with the charging voltage under 3V, and can be cycled stably for more than 50 cycles.

Embodiment 2

[0071] The embodiment relates to a high voltage rechargeable Zn—MnO.sub.2 battery, which has the structure of zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode. The specific preparation steps are as follows.

[0072] 1) Preparation of the zinc electrode, in which 10 g of zinc powder is added into 4 g of lithium hydroxide solution with a mass fraction of 20 wt %, together with 0.04 g of sodium polyacrylate adhesive, then the mixture is stirred evenly and left at room temperature for 12 hours to obtain a pasted zinc electrode.

[0073] 2) Preparation of the alkaline liquid electrolyte, in which 20 g of lithium hydroxide and 4 g of zinc oxide are dissolved in 100 mL of deionized water to obtain the alkaline liquid electrolyte.

[0074] 3) Ion exchange membrane, in which the ion exchange membrane of the high-voltage Zn—MnO.sub.2 battery system of the present embodiment may be a proton exchange membrane, an anion exchange membrane, a cation exchange membrane or the like. Specifically, in this embodiment, a quaternary ammonium anion exchange membrane is employed.

[0075] 4) Preparation of the acidic liquid electrolyte, in which 10 g of phosphoric acid and 20 g of manganese sulfate monohydrate are dissolved in 100 mL of water to obtain an acidic liquid electrolyte.

[0076] 5) Preparation of the electrodeposited MnO.sub.2 electrode, in which 20 g of manganese sulfate monohydrate and 20 g of sulfuric acid are dissolved in 100 mL of water, and a graphite sheet is employed as the working electrode and the counter electrode. Upon using a DC power source to deposit at 1.8V for 3600 seconds, the anode piece in the electrolytic cell is taken out, rinsed, and dried, thus resulting in an electrodeposited MnO.sub.2 electrode.

[0077] 6) Battery assembly, in which the battery is formed in the structure of zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode in combination.

[0078] The resulted battery has an open circuit voltage above 2.6V, and a working platform voltage above 2.4V. The resulted battery can be charged and discharged, with the charging voltage under 3V, and can be cycled stably for more than 1000 cycles.

Embodiment 3

[0079] The embodiment relates to a high voltage rechargeable Zn—MnO.sub.2 battery, which has the structure of zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode. Its specific preparation steps are as follows.

[0080] 1) Preparation of the zinc electrode, in which 80 g of zinc powder, 10 g of graphite, 10 g of polyvinylidene fluoride, 4 mL of N-methylpyrrolidone are uniformly mixed, and dried to obtain a zinc powder electrode.

[0081] 2) Preparation of the alkaline gel electrolyte, in which lg of polyvinyl alcohol powder is dissolved in 30 mL of water, stirred at 95° C. for 3 hours, and then the mixture is added with 0.05 g of potassium persulfate powder, and retained at 65° C. for 15 minutes to obtain solution 1.

[0082] Another 10 g of acrylic acid is mixed with 10 g of sodium hydroxide solution with a mass fraction of 40 wt %, and the mixture is added with 0.05 g of NN′-methylenebisacrylamide, stirred evenly, resulting in solution 2.

[0083] The solutions 1, 2 are uniformly mixed, and retained at 75° C. by water bath for 3 hours to obtain a gel. The gel is then immersed in a lithium hydroxide solution with a mass fraction of 10 wt % for 24 hours to obtain a polyacrylic acid-polyvinyl alcohol-lithium hydroxide electrolyte having a lithium hydroxide concentration of 100 g/L.

[0084] 3) Ion exchange membrane, in which the ion exchange membrane of the high voltage Zn—MnO.sub.2 battery system of the present embodiment may be a proton exchange membrane, an anion exchange membrane, a cation exchange membrane or the like. Specifically, in the present embodiment, a sulfonic acid based proton exchange membrane is employed.

[0085] 4) Preparation of the acidic liquid electrolyte, in which 10 g of sulfuric acid and 15 g of manganese sulfate monohydrate are dissolved in 100 mL of water to obtain an acidic liquid electrolyte.

[0086] 5) Preparation of the MnO.sub.2 electrode, in which 8 g of MnO.sub.2 powder is uniformly mixed with lg of graphite powder and 1 g of polyvinylidene fluoride, and then the mixture is added with 0.4 g of 100 g/L sulfuric acid solution, stirred, and dried to serve as a MnO.sub.2 electrode.

[0087] 6) Battery assembly, in which the battery is formed in the structure of zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode in combination.

[0088] The resulted battery has an open circuit voltage above 2.6V, and a working platform voltage above 2.4V. The resulted battery is chargeable and dischargeable, with the charging voltage under 3V, and can be cycled stably for more than 100 cycles.

Embodiment 4

[0089] The embodiment relates to a high voltage rechargeable Zn—MnO.sub.2 battery, which has the structure of zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode. Its specific preparation steps are as follows.

[0090] 1) Preparation of the zinc electrode, in which 10 g of zinc powder is added to 4 g of potassium hydroxide solution with a mass fraction of 40 wt %, together with 0.04 g of sodium polyacrylate adhesive, and the mixture is stirred evenly, retained at room temperature for 12 hours to obtain a zinc paste electrode.

[0091] 2) Preparation of the alkaline liquid electrolyte, in which 35 g of potassium hydroxide and 4 g of zinc acetate are dissolved in 100 mL of deionized water to obtain an alkaline liquid electrolyte.

[0092] 3) Ion exchange membrane, in which the ion exchange membrane of the high voltage Zn—MnO.sub.2 battery system of the present embodiment may be a proton exchange membrane, an anion exchange membrane, a cation exchange membrane or the like, and specifically in the present embodiment, a sulfonic acid based proton exchange membrane is employed.

[0093] 4) Preparation of the acidic liquid electrolyte, in which 10 g of sulfuric acid and 15 g of manganese sulfate monohydrate are dissolved in 100 mL of water to obtain an acidic liquid electrolyte.

[0094] 5) Preparation of the electrodeposited MnO.sub.2 electrode, in which 20 g of manganese sulfate monohydrate and 20 g of sulfuric acid are dissolved in 100 mL of water, and a graphite sheet is employed as a working electrode and a counter electrode. Upon using a DC power source to deposit at 1.8V for 3600 seconds, the anode piece in the electrolytic cell is taken out, rinsed, and dried, thus resulting in an electrodeposited MnO.sub.2 electrode.

[0095] 6) Battery assembly, in which the battery is formed in a structure of zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode in combination.

[0096] As shown in FIG. 2, the resulted battery has an open circuit voltage above 2.7V, and a working platform voltage above 2.65V. As shown in FIG. 3, the resulted battery is chargeable and dischargeable, with the charging voltage under 3V, and can be cycled stably for more than 100 cycles.

Embodiment 5

[0097] The embodiment relates to a high voltage rechargeable Zn—MnO.sub.2 battery, which has the structure of zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode. Its specific preparation steps are as follows.

[0098] 1) Preparation of the zinc electrode, in which 10 g of zinc powder is added into 4 g of potassium hydroxide solution with a mass fraction of 40 wt %, together with 0.04 g of sodium polyacrylate adhesive, and the mixture is uniformly stirred, retained at room temperature for 12 hours, thus resulting in a zinc paste electrode.

[0099] 2) 1 g of polyvinyl alcohol powder is dissolved in 30 mL of water, heated and stirred at 95° C. for 3 hours, and then the mixture is added with 0.05 g of potassium persulfate powder, and retained at 65° C. for 15 minutes to obtain solution 1.

[0100] Another 10 g of acrylic acid is mixed with 10 g of sodium hydroxide solution with a mass fraction of 40 wt %, and further added with 0.05 g of NN′-methylenebisacrylamide, and the mixture is stirred evenly, thus resulting in solution 2.

[0101] The solutions 1, 2 are uniformly mixed, and retained at 75° C. by water bath for 3 hours to obtain a gel. The gel is then immersed in 250 g/L potassium hydroxide+40 g/L zinc acetate solution for 24 hours to obtain a polyacrylic acid-polyvinyl alcohol-potassium hydroxide-zinc acetate electrolyte.

[0102] 3) Ion exchange membrane, in which the ion exchange membrane of the high voltage Zn—MnO.sub.2 battery system of the present embodiment may be a proton exchange membrane, an anion exchange membrane, a cation exchange membrane or the like, and specifically in the present embodiment, a sulfonic acid based proton exchange membrane is employed.

[0103] 4) Preparation of the acidic gel electrolyte, in which 3 g of polyvinyl alcohol is heated and dissolved in 24 mL of water to form a uniform and stable solution, and then the solution is poured into 6 mL of 500 g/L sulfuric acid+250 g/L manganese sulfate monohydrate solution. After stirring evenly, the resulted solution is placed in a freezer. Then it is taken out to melt for use, resulting in a polyvinyl alcohol-sulfate-manganese sulfate electrolyte having a sulfuric acid concentration of 100 g/L in the liquid portion and a manganese sulfate concentration of 50 g/L.

[0104] 5) Preparation of the MnO.sub.2 electrode, in which 8 g of MnO.sub.2 powder is uniformly mixed with 1 g of graphite powder and lg of polyvinylidene fluoride, and then the mixture is added with 0.4 g of a 100 g/L sulfuric acid solution, stirred, and dried to serve as a MnO.sub.2 electrode.

[0105] 6) Battery assembly, in which a battery is formed in a structure of zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode in combination.

[0106] The resulted battery has an open circuit voltage above 2.7 V, and a working platform voltage above 2.6 V. The resulted battery is chargeable and dischargeable, with the charging voltage under 3V, and can be cycled stably for more than 50 cycles.

Embodiment 6

[0107] The embodiment relates to a high voltage rechargeable Zn—MnO.sub.2 battery, which has the structure of zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode. Its specific preparation steps are as follows.

[0108] 1) Preparation of the zinc electrode, in which 80 g of zinc powder, 10 g of graphite, 10 g of polyvinylidene fluoride, 4 mL of N-methylpyrrolidone are uniformly mixed, and dried to obtain a zinc powder electrode.

[0109] 2) Preparation of the alkaline gel electrolyte, in which 1 g of polyvinyl alcohol powder is dissolved in 30 mL of water, heated and stirred at 95° C. for 3 hours, then the mixture is added with 0.05 g of potassium persulfate powder, retained at 65° C. for 15 minutes to obtain solution 1.

[0110] Another 10 g of acrylic acid is mixed with 10 g of sodium hydroxide solution with a mass fraction of 40 wt %, and the mixture is added with 0.05 g of NN′-methylenebisacrylamide, stirred uniformly, to obtain solution 2.

[0111] The solutions 1, 2 are uniformly mixed, and retained at 75° C. by water bath for 3 hours to obtain a gel. The gel is then immersed in 250 g/L potassium hydroxide+40 g/L zinc acetate solution for 24 hours to obtain a polyacrylic acid-polyvinyl alcohol-potassium hydroxide-zinc acetate electrolyte.

[0112] 3) Ion exchange membrane: the ion exchange membrane of the high voltage Zn—MnO.sub.2 battery system of the present embodiment may be a proton exchange membrane, an anion exchange membrane, a cation exchange membrane or the like, and specifically in the present embodiment, a sulfonic acid based proton exchange membrane is employed.

[0113] 4) Preparation of the acidic liquid electrolyte, in which 10 g of sulfuric acid and 15 g of manganese sulfate monohydrate are dissolved in 100 mL of water to obtain an acidic liquid electrolyte.

[0114] 5) Preparation of the MnO.sub.2 electrode, in which 8 g of MnO.sub.2 powder is uniformly mixed with 1 g of graphite powder and 1 g of polyvinylidene fluoride, and then the mixture is added with 0.4 g of 100 g/L sulfuric acid solution, stirred, and dried to serve as the MnO.sub.2 electrode.

[0115] 6) Battery assembly, in which the battery is formed in the structure of zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode in combination.

[0116] The resulted battery has an open circuit voltage above 2.7 V, and a working platform voltage above 2.6 V. The resulted battery is chargeable and dischargeable, with the charging voltage under 3V, and can be cycled stably for more than 100 cycles.

Embodiment 7

[0117] The embodiment relates to a high voltage rechargeable Zn—MnO.sub.2 battery, which has the structure of zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode. Its specific preparation steps are as follows.

[0118] 1) Preparation of the zinc electrode, in which 10 g of zinc powder is added into 4 g of potassium hydroxide solution with a mass fraction of 40 wt %, together with 0.04 g of sodium polyacrylate adhesive, and the mixture is uniformly stirred, retained at room temperature for 12 hours to obtain the zinc paste electrode.

[0119] 2) Preparation of the alkaline liquid electrolyte, in which 35 g of potassium hydroxide and 4 g of zinc acetate are dissolved in 100 mL of deionized water to obtain the alkaline liquid electrolyte.

[0120] 3) Ion exchange membrane, in which the ion exchange membrane of the high voltage Zn—MnO.sub.2 battery system of the present embodiment may be a proton exchange membrane, an anion exchange membrane, a cation exchange membrane or the like, and specifically in the present embodiment, a sulfonic acid based proton exchange membrane is employed.

[0121] 4) Preparation of the acidic gel electrolyte, in which 3 g of polyvinyl alcohol is heated and dissolved in 24 mL of water to form a uniform and stable solution, and then it is poured into 6 mL of 500 g/L sulfuric acid+250 g/L manganese sulfate monohydrate solution. After stirring evenly, the resulted solution is placed in a freezer. Then it is taken out to melt for use, resulting in a polyvinyl alcohol-sulfate-manganese sulfate electrolyte having a sulfuric acid concentration of 100 g/L in the liquid portion and a manganese sulfate concentration of 50 g/L.

[0122] 5) Preparation of the MnO.sub.2 electrode, in which 8 g of MnO.sub.2 powder is uniformly mixed with 1 g of graphite powder and 1 g of polyvinylidene fluoride, and then the mixture is added with 0.4 g of a 100 g/L sulfuric acid solution, stirred, and dried to serve as the MnO.sub.2 electrode.

[0123] 6) Battery assembly, in which the battery is formed in a structure of zinc electrode/alkaline electrolyte/ion exchange membrane/acid electrolyte/MnO.sub.2 electrode in combination.

[0124] The resulted battery has an open circuit voltage above 2.7V, and a working platform voltage above 2.6V. The resulted battery is chargeable and dischargeable, with the charging voltage under 3V, and can be cycled stably for more than 100 cycles.

[0125] The specific embodiments of the present invention have been described above. It is to be understood that the invention is not limited to the specific embodiments described above, and various modifications and changes may be made by those skilled in the art without departing from the scope of the invention, which do not affect to the substantive content of the invention.

[0126] The foregoing description of the exemplary embodiments of the present invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.

[0127] The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to activate others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.