When the Prius first hit the market in 2000, Toyota used a nickel metal hydride (NiMH) battery pack to power the car. In 2015, they began opting for a lithium-ion battery pack instead for its lighter weight and higher energy-storing capacity. NiMH batteries were still used after 2015, though, mostly in all-wheel drivetrains.
So, if you check your owner’s manual and see that you’ve got a NiMH battery powering your Prius, you may want to seriously consider getting a new aftermarket battery. Chances are, if you’ve got one with this kind of battery, its 10 year / 100,000 warranty is nearly up, anyways. Although it will cost you a decent chunk of change, it may be worth it to help keep your vehicle on the road longer as opposed to purchasing a new one outright.