Batteries

There are 3 main types of battery:

Primary cell: use once and then discard. Leclanche cells Alkaline cells Lithium batteries

Secondary cell: rechargeable as redox reaction is reversible.

Pb/Acid NiCd Lithium ion

Flow Batteries / Fuel Cells

Georges Leclanché (1839-1882)

battery : Zinc–manganese dioxide Systems  These batteries are the most commonly used worldwide in flashlights, toys, radios, compact disc players, and digital cameras. There are three variations: the zinc-carbon battery, the zinc chloride battery, and the alkaline battery. All provide an initial voltage of 1.55 to 1.7 volts.

The redox reaction that the battery relies on is the oxidation of the Zinc and the reduction of the manganese:

Zn Zn2+ + 2e-MnO2 + 2H2O + 2e- 2MnOOH

+2OH-

A electrolytic cell also known as a dry cell that uses a moist paste rather than a liquid as an electrolyte. Flashlight batteries are dry cells with a zinc cup for an anode, a carbon rod for a cathode, and a paste made of powdered carbon, NH4Cl, ZnCl2, and MnO2 for an electrolyte.

Zn + 2 MnO2 + 2 NH4Cl -> ZnCl2 + Mn2O3 + 2 NH3 + H2O

Pb + H2SO4 ==> PbSO4 + 2e + 2H+ (Anode)PbO2 + H2SO4+ 2e + 2H+ ==> PbSO4 + 2H2O (Cathode)

PbO2 +2 H2SO4+ Pb ==> 2PbSO4 +2H2O

How a Fuel Cell Works

H2(g) = 2H+ + 2e- (anode)

2H+ + 1/2 02 (g) + 2e- = H20 (cathode )

The overall fuel cell reaction then is simply:

H2 + 1/2 02 = H20