This document discusses four main types of cells: 1) Dry cells, which store chemical energy in an immobilized electrolyte paste and are used in cameras, clocks, toys, and radios. 2) Mercury cells, also called mercury oxide batteries, which use a reaction between mercuric oxide and zinc in an alkaline electrolyte and are used in watches, calculators, and electronic instruments. 3) Nickel-cadmium cells, which are rechargeable and use nickel oxide hydroxide and cadmium as electrodes, being used in watches, calculators, and electronic instruments. 4) Lithium-ion cells, which are also rechargeable and involve the movement of lith