The Nokia Lumia 920 sports the largest battery capacity Nokia’s put in a phone, at 2000mAh. Something not mentioned in the specifications is what type of battery. Nokia batteries are almost often lithium-ion. In wikipedia’s own entry, the battery to depict all Li-ion is a Nokia battery.
The disadvantages noted for Li-ion are cell life, so over time, the capacity of the battery decreases. e.g. what may get you a minimum of 2 days in your first month might end up with half a day a year or two later. The article above also describes other pros and cons.
Lithium-ion polymer or lithium polymer (LiPo) batteries is described as evolving from Li-ion batteries.
It allows batteries to fit in more unusual/slimmer places as well as reducing the aging effect. This is supposedly the type of battery found in the Nokia Lumia 920. If the image is correct, then the Lumia 920 has a 2000mAh LiPo battery.
The Nokia Lumia 900 also has a LiPo battery, with 1830mAh battery capacity. Only 170 less than the 920 but sporting a smaller 4.3″ screen (vs 4.5). The 3.7″ Nokia Lumia 800 and 710 have Li-ion batteries.
Bigger batteries and battery types aren’t the only things important in battery life. How the phone itself consumers these resources play a huge role too. How big is the screen, what type of screen, how bright, how often does it connect to the internet, what background processes does it run, how efficient the OS is, how fun it is to use therefore you might be using it all the time (or never).
In the Nokia Lumia 920, we’ve been told that there’s been quite a bit of battery saving improvements too to get you over a day’s use.
Cheers anonymous for the tip!