Lithium batteries are literally the powerhouse behind the mobile gadget revolution: They're reliable, they don't have a serious multiple-cycle "memory effect" like Ni-Cad batteries do, they can be fashioned into all sorts of shapes, and they're good a providing significant amounts of charge. But they're far from perfect--a fuss about their fire-hazard habits is in the headlines right now, for example. This is because they're actually very sophisticated inside, and the electrolyte the lithium is dissolved in is often toxic and flammable.
But now scientists have found a way to remove some of the barriers that prevent an alternative tech--aqueous lithium ion batteries--working as efficiently, and in the future these power cells may take up some of the load of "normal" lithium ion batteries. The advantage of an aqueous Li-ion cell are obvious right there in the name: They're water based, and thus potentially less poisonous and explodey. The tech's been in existence for a while, but never seen mainstream adoption due to the very, very poor lifespan of the design. It's typical to see the capacity of an aqueous unit fall to less than 50% of charge after just a thousand cycles.
Which is where the clever bit of new thinking comes in. By tweaking the oxygen content in a lithium sulphate/water electrolyte, the team discovered that the cells retained up to 90% of their capacity after a thousand cycles--much closer to the performance of more "normal" Li-cells. A few drawbacks do remain, though: The power retention of the devices is reduced. The developers see that the system could have uses in situations where its safety is desirable though, such as hybrid-engine city buses, or where wind turbines or other alt-power generators are producing spare electrical capacity that needs to be stored.
iPad Li-ion battery image via iFixit