Lithium crystal circuit

From Memory Alpha, the free Star Trek reference.

The lithium crystal circuit was part of the power generation system of Starfleet vessels in 2266.

Over expenditures of power could damage the vital lithium crystals at the heart of these circuits. In 2266, the USS Enterprise pursued an unregistered cargo ship into an asteroid belt. Forced to extend her shields around the cargo ship overloaded the power generating circuitry and burned out three of the four lithium crystal circuits. The fourth failed subsequently, overstressed from handling all of the ship's power. (TOS: "Mudd's Women")

The relation of a lithium crystal to a dilithium crystal has never been explained. It is possible its use was replaced by dilithium, or it could have been a related component.