From what I've read, the battery life is measured in full recharge cycles. They can be fully recharged, 300 times, 500 times, etc. Let's say that the batteries take 5 hours to charge, and you can go 100 miles. If you charge them for 2.5 hours, that's only a half cycle.
They are starting to wire together lithium-ion cells (like the ones used in laptop computers) because they produce higher output, last longer, and have more recharge cycles. I think the Tesla Roadster has 16,000 LI cells wired together into one big 900lb battery. It can go 0-60 in 4 seconds, travels over 200 miles on a charge, and can exceed 130mph.