The difference between a cell and a battery is that a cell is a single unit that converts chemical energy into electrical energy, and a battery is a collection of cells. According to About.com expert Mary Bellis, each cell contains two electrodes and an electrolyte, a substance that reacts chemically with each electrode, generating an electrical current. Aggregating cells into a battery increases the electrical voltage they produce.
Batteries are classified by electrolyte type. "Dry cell" batteries contain electrolytes dispersed in a dry or porous substance packed between the two electrodes. In a "wet cell" battery, the electrolyte is a free-flowing liquid. According to the United States Environmental Protection Agency, wet cell batteries contain caustic chemicals that burn skin and release dangerous fumes. They also contain lead, which is toxic to people and animals and contaminates groundwater.
Small batteries, such as those that power portable electronics, are usually disposable. These batteries have a single charge and require replacement after depletion. When rechargeable batteries are drained, however, they require connection to an external power source. After charging, the batteries are ready for reuse. Rechargeable batteries are commonly found in automobiles, laptop computers and mobile phones.
According to the Mother Nature Network, disposable alkaline batteries are not environmentally hazardous and most municipalities encourage residents to discard them in household trash. Other batteries, particularly of the wet cell type, contain heavy metals and dangerous substances capable of causing serious harm to the environment, people and animals. These batteries do not belong in regular municipal garbage facilities and must be recycled or discarded according to local laws.