U can read complete informations about Lithium batterys here: http://www.batteryuniversity.com/parttwo-34.htm
But, anyway its better to format it 3 times....better safe then sorry.Some studies concluded that the battery will wear out faster if you dont format it....And except somr time you got nothing to lose.
Hope it helps.
Phones i owned so far 6630,6680,N90,N93*