I don't know, but there seems to be not very much incentive to invest a lot of R&D dollars on this problem from a manufacturer standpoint:

* Devices marketed on how long they last on a single charge, but much less often on how quickly the battery degrades * Batteries are a later upgrade upsell opportunity * I would not be surprised to learn that a significant number of device upgrades start as simply wanting a better battery (but why not upgrade at the same time)