Lithium-Ion Tool Battery: Preferred for high power density and long life. 

The lithium-ion battery is the undisputed champion of modern power tool technology. It has replaced older battery types due to its superior performance characteristics. Unlike NiCd batteries, which suffer from a "memory effect" that reduces their capacity if they're not fully discharged before recharging, lithium-ion batteries can be charged at any time without negative consequences.

The advantages of lithium-ion batteries are numerous. They have a high energy density, which means they can store more power in a smaller, lighter package. This results in tools that are easier to handle and less fatiguing to use. They also have a low self-discharge rate, allowing them to hold their charge for longer when not in use. Additionally, they provide a more consistent power output throughout their discharge cycle, ensuring the tool maintains peak performance until the very end. The development of advanced lithium-ion technologies, such as stacked battery cells and sophisticated battery management systems (BMS), continues to push the boundaries of power, runtime, and safety.