Battery tech hasn't changed much, there getting slimmer and also harder to replace as most are internal. Most of the Lenovo laptop I work have 2 batteries.
But the tech inside the laptop have change. meaning they use less energy so the battery life improves. most laptop these days should have at least 4.5 - 6 hours battery life (depending on what your doing on the laptop). Think my Mac has around 6 hours life and charges very quick.
It sounds exactly as Micro said above, I think ur battery as 3 cells and 1 or maybe 2 of them have died, so basically your battery can no longer handle the power requirement your laptop needs.