|Some explanation about lithium-ion batteries, the one used in your laptop:|
"Aging is a concern with most lithium-ion batteries and many manufacturers remain silent about this issue. Some capacity deterioration is noticeable after one year, whether the battery is in use or not. The battery frequently fails after two or three years. It should be noted that other chemistries also have age-related degenerative effects. This is especially true for nickel-metal-hydride if exposed to high ambient temperatures. At the same time, lithium-ion packs are known to have served for five years in some applications."
Having used laptops for professional since the 90's, I already experienced this effect of broken or aging batteries. Five years for a laptop-battery is an extreme exception for me.