Researchers at Japan’s AIST (National Institute of Advanced Industrial Science and Technology) report the development of a new type of lithium-copper air fuel cell using a hybrid electrolyte (organic electrolyte/solid electrolyte/aqueous electrolyte).
A copper positive electrode is placed in the aqueous electrolyte and metallic lithium is used as a negative electrode in the organic electrolyte. The copper electrode is oxidized by oxygen in the air to generate copper (I) oxide (Cu2O). Upon discharge, lithium atoms of the negative electrode supply electrons to the wire and dissolve as lithium ions, which go through the solid electrolyte towards the aqueous electrolyte.
At the positive electrode, supplied electrons reduce Cu2O molecules to copper atoms that precipitate on the electrode. After the discharge, copper is oxidized again through copper-corrosion reaction. In this way, oxygen is electrochemically reduced and copper works as catalysts of the oxygen reduction. The developed lithium-copper air fuel cell based on this copper-corrosion reaction shows stable discharge.
|Li-Cu air fuel cell. Click to enlarge.|
Earlier, AIST reported the development of a novel secondary battery with metal Cu positive electrode and metal Li negative electrode. The battery uses an aqueous electrolyte for the Cu cathode and a non-aqueous electrolyte for the Li anode, connected together by a glassy state electrolyte film through which only lithium ions can pass.
During the charge and discharge processes, the dissolution-deposition of the Cu (or Li) electrode and the transfer of lithium ions between aqueous electrolyte solution and non-aqueous solution occurs. The highly reversible dissolution-deposition process of Cu metal positive electrode results in a capacity of 843 mAh g-1, which is much higher than those of conventional positive electrodes. The active electrode materials of this new type of Li-Cu secondary battery are recyclable.