AIST developing lithium-copper air fuel cell
20 February 2011
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.
At what voltage????
This sounds very interesting, but at .5V it is mildly interesting. At 4V, 843mAh/g is game changing.
So I'm guessing it's not that good or they would be bragging about it in bold red headlines.
Of course, we also need to talk about cost, power, cycle life, shelf life, safety, yada, yada, yada.
I've said it before, I'll say it again: Never trust any battery or fuel cell announcement that doesn't include enough info to tell you if it's really a breakthrough or just another curiosity in the lab.
Posted by: DaveD | 20 February 2011 at 01:32 PM
Oops, my bad. I didn't look at the graph, just read the story. At ~2.6V at 843mAh/g gives the cathode an energy density of around 2,200Wh/kg. That is just for the cathode and a pack built around it would probably be about 1/3 of that in reality, but still great stuff.
Of course, my other questions still remain: what cost, power density, cycle life, shelf life, safety, etc.
Posted by: DaveD | 20 February 2011 at 06:05 PM
The 843 mAh/g is not for the copper-air battery. Capacity for this is likely to be higher. I would like to know what is it and also the current capacity. Typical metal-air batteries have such low current capacity, they are impractical for cars.
Posted by: Zhukova | 22 February 2011 at 09:08 AM
The voltage graph shows a steady-state voltage of about 2.5V, so the electrode yields about 2.2 Wh/g.
Zhukova may be right about the rate; the test ran for 30 hours, and the internal resistance may be much too high for 3C or even 1C discharge rates. Then there's charging...
Would charging of a metal-air battery in an enclosed space raise the oxygen concentration enough to create a fire hazard?
Posted by: Engineer-Poet | 23 February 2011 at 06:02 PM