The linked article does not provide details. However, Engadget has an article on this that offers this tidbit: "The aluminum-ion cell isn't perfect (yet) as it

The linked article does not provide details. However, Engadget has an article on this that offers this tidbit: "The aluminum-ion cell isn't perfect (yet) as it can only produce about 2 volts, far less than the 3.6V that lithium-ion an muster. Plus aluminum cells only carry 40 watts of electricity per kilogram compared to lithium's 100 to 206 W/kg power density." http://www.engadget.com/2015/04/06/stanfords-battery-charges-in-one-minute/ http://www.engadget.com/2015/04/06/stanfords-battery-charges... Sidenote: I suspect that passage means W-hours per Kg vs. W per Kg because typical Li-ion does have an energy density in the 100-200 W-h/kg range. See the chart in this Nature article: http://www.nature.com/news/the-rechargeable-revolution-a-better-battery-1.14815 http://www.nature.com/news/the-rechargeable-revolution-a-bet...