which cuts down on the weight - I presume zinc-air batteries aren't rechargeable, as this one is.
An article with one or two more technical details:
Rechargeable lithium batteries are currently comprised of a graphite negative electrode, an organic electrolyte and lithium cobalt oxide as the positive electrode. Lithium is removed from the layered intercalation compound (lithium cobalt oxide) on charging and re-inserted on discharge.
Energy storage is limited by the lithium cobalt oxide electrode (0.5 Li/Co, 130 mAhg-1). The University of St Andrews design replaces the lithium cobalt oxide electrode with a porous carbon electrode and allows Li+ and e- in the cell to react with oxygen from the air.
Initial results from the project found a capacity to weight ratio of 1,000 milli-amp / hours per gram of carbon (mA/hours/g), while recent work has obtained results of up to 4,000 mA/hours/g. Although the two designs work very differently, this equates to an eight-fold increase compared to a standard cobalt oxide battery found in a mobile phone.
http://insciences.org/article.php?article_id=5065It would appear the carbon doesn't take part in a chemical reaction, but its just there to give a structure; and I presume that when the battery is recharged, it gives off the oxygen that went into the lithium/oxygen compund during discharge, while the lithium becomes a lithium ion again.