@trinsec I think it's a tradeoff between energy density and shelf stability. If you build a battery using a really energetically favourable reaction to get more mAh into the same dimensions, it seems plausible that the reagents will be more difficult to keep from reacting in ways you don't want, too. But both sides of the tradeoff can be marketed as lasting longer - if you change batteries in response to energy exhaustion, a more energy-dense battery will have longer lives in practice; but if they have plenty of charge until they physically fail, you'll have to replace more shelf-stable ones less frequently.