Yes, almost all modern Philips Sonicare electric toothbrushes are equipped with lithium-ion (Li-ion) batteries. Unlike older nickel-metal hydride (NiMH) batteries, lithium-ion versions do not suffer from the "memory effect" and offer a significantly higher energy density. This allows Sonicare brushes to maintain a full power stroke consistently until the battery is nearly depleted, typically providing about two to three weeks of brushing on a single charge. Because lithium batteries are sensitive to extreme temperatures and deep discharge, it is recommended to keep the brush on its charger or recharge it regularly rather than waiting for it to die completely. For travel, the inclusion of lithium batteries means the toothbrush must be packed in your carry-on luggage if you are taking it on an airplane, as lithium batteries are prohibited in checked bags due to flight safety regulations.