Nonvolatile BIOS memory. NEC D4364G 8192 x 8 Bit Static CMOS RAM. CMOS battery in a Pico ITX motherboard. Type CR2032 button cell, most common CMOS battery.
These are made of several distinct battery technologies and here are a few popular technologies among the lot: Nickel Cadmium (NiCd) Nickel Metal Hydride (NiMH) Lithium Ion (Li-ion) Lithium Ion Polymer (Li-ion polymer)