Hitachi have developed a battery that is capable of lasting 10 years. Current Li-ion batteries we hear are good for about 5 years at the most until they stop holding their charge and become useless. Our own experience shows this is actually a bit less at around 3 - 4 years.
The new batteries use a new cathode material that contains manganese and is then locked together with substances to make it more stable. What this method achieves is less bleed from the cathode in to the electrolyte material (ie, the problem that causes regular li-ion batteries to die after a few years).
Although leakage still occurs, Hitachi have managed to slow this down allowing the battery to work for up to double the amount of time (in this case a claim of 10 years has been made).
You might wonder why this is important though considering the speed at which we go through gadgets. I have always replaced gadgets such as laptops before the battery becomes a real issue as do many other people. The real benefit of longer lasting li-ion batteries could be in wind-farms that tend to stand for years where the batteries are used to store energy generated by wind according to Wired. Also other installations where technology doesn't necessarily expire as quick as the gadget world would be ideal for using such batteries.
What we wont get from this is longer battery life per charge it seems. It appears that we will still need to recharge gadgets after several hours of use.
For the full run down of how this works check out Hitachi.