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An electrochemical cell including a cathode, an electrolyte in ionic contact with the cathode, and an anode in physical contact with the electrolyte, wherein the anode contains a controlled release anode composition that includes at least a first anode active material and at least a first controlled

An electrochemical cell including a cathode, an electrolyte in ionic contact with the cathode, and an anode in physical contact with the electrolyte, wherein the anode contains a controlled release anode composition that includes at least a first anode active material and at least a first controlled release agent in physical contact thereto for tentatively isolating the first anode active material from the electrolyte in the beginning of a cell operation for a delayed reaction of the first anode active material. Preferably, the anode further contains an initial-stage anode active material in direct contact with the electrolyte. Such a controlled release anode can be used in a variety of electrochemical cells including metal-air batteries, such as a zinc-air battery, for an extended period of operating time.

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1. A metal-air electrochemical cell comprising an oxygen cathode, an electrolyte an ionic contact with said oxygen cathode, and an anode in physical contact with said electrolyte, whereinsaid anode comprises a controlled release anode composition that comprises at least a first anode active metal ma

1. A metal-air electrochemical cell comprising an oxygen cathode, an electrolyte an ionic contact with said oxygen cathode, and an anode in physical contact with said electrolyte, whereinsaid anode comprises a controlled release anode composition that comprises at least a first anode active metal material and at least a first controlled release agent in physical contact thereto for tentatively isolating said first anode active material from said electrolyte in the beginning of a cell operation for a delayed oxidation of said first anode active material. 2. The electrochemical cell as set forth in claim 1, wherein said anode further comprises an initial-stage anode active material in direct contact with said electrolyte.3. The electrochemical cell as set forth in claim 1 or 2, wherein said first anode active material comprises a metallic element selected from the group consisting of lithium, magnesium, aluminum, titanium, manganese, iron, chromium, nickel, and zinc.4. The electrochemical cell as set forth in claim 1 or 2, wherein said controlled release agent contains a material selected from the group consisting of a polymer, a ceramic, a glass, a carbon, an organic, a metallic material, and combinations thereof.5. The electrochemical cell us set forth in claim 1 or 2, wherein said first anode active material is in a form of fine particles that are coated, plated, embedded or encapsulated with said controlled release agent.6. The electrochemical cell as set forth in claim 1 or 2, wherein said first anode active material is in a fibrous, plate-like, disc-like, rod-like, or needle-like form which is coated, plated, embedded or encapsulated with said controlled release agent in such a way that said first anode active material is separated from said electrolyte during an initial stage of a cell operation.7. The electrochemical cell as set forth in claim 2, wherein said first anode active material differs in chemical composition from said initial-stage anode active maternal.8. The electrochemical cell as set forth in claim 2, wherein said initial-stage anode active material comprises zinc and said first anode active material contains a metallic element selected from the group consisting of lithium, magnesium, aluminum, titanium, manganese, iron, chromium, nickel, and zinc.9. The electrochemical cell as set forth in claim 1 or 2, wherein said first anode active material is coated or encapsulated with said first controlled release agent by a technique selected from the group consisting of electroplating, electrodeless costing, electrochemical deposition, physical vapor deposition, chemical vapor deposition, plasma deposition, organic phase separation, surface polymerization, solution coating, solvent casting, fluidized bed coating, thermal spraying, solution spraying, and combinations thereof.10. The electrochemical cell as set forth in claim 1 or 2, wherein said first anode active material is coated or encapsulated with said first controlled release agent comprising a metal having an electromotive force smaller than the electromotive force of said first anode active material but greater than the electromotive force of an oxygen half cell.11. The electrochemical cell as set forth in claim 1 or 2, wherein said first anode active material is fully coated or encapsulated with said first controlled release agent, said agent comprising a metal with a small electromotive force selected from the group consisting of nickel, tin, lead, antimony, bismuth, and indium.12. The electrochemical cell as set forth in claim 1 or 2, wherein controlled release is achieved through the mechanism selected from the group consisting of desorption, diffusion, erosion, wear or destruction of a barrier material, degradation, chemical reaction, hydrolysis, thermodynamic dissociation, and combinations thereof.13. A multiple-cell battery assembly comprising a plurality of electrochemical cells, wherein at least one of said cells is a cell as defined in claim 1 or 2.14. The electrochemical cell as set forth in claim 1 or 2, wherein said electrolyte is substantially force from a liquid during a cell storage period and said cell is actuated when a liquid is added to said electrolyte.15. The electrochemical cell as set forth in claim 14, wherein said liquid comprises water.