Really high actually, if the performance is true.
OXIS Energy are a small company based in Oxfordshire specialising in the lithium-sulfur battery system – which naturally I’m very interested in, since this is the field I’ve worked in for the last two years. They are also probably one of the leading industrial developers of the Li-S system, along with Sion Power in the US. However, in the six years or so that I’ve been aware of their existence, the improvement in the technology hasn’t quite followed the bold predictions. For a long time it seemed that OXIS could not push much past an energy density of 200 Wh/kg – more or less equivalent to the current lithium-ion technology. Sion Power, on the other hand, have for some time been able to boast of cells with an energy density of 350 Wh/kg, but with a relatively short cycle life.
Yesterday, however, OXIS announced via a press release that their cells now reach past 300 Wh/kg, that they can make huge cells with a capacity of 25 Ah (roughly the energy of the average laptop battery, but only 1 cell rather than 6, and half the weight), and, based on their technology page, an expected lifetime of the order of 2000 cycles.
That’s an enormous improvement since just a couple of years ago and could (should?) make these cells competitive with Li-ion for a pretty wide range of applications, so I think I will be keeping a closer eye on their press releases from now on…