These are source of electrical energy which may have one or more cells connected in series. For a good quality of battery, should be reasonably light, compact and its voltage should no very appreciably during its use.
Primary Batteries : In the primary batteries, the reaction occurs only once and after use over a period of time, battery become dead and cannot be reused again.
e.g. Leclanche cell
Some common example of primary cells are given below :
Dry Cell : The working of a dry cell is based on electrolysis.
The depolariser used in dry cell is MnO2.
The internal resistance of a dry cell is higher than that of electrolyte cell. It is commonly used in transistors, clocks etc. It is a compact form of Leclanche cell.
Zinc container act as anode and graphite rod acts as cathode.
Graphite rod is surrounded by powdered MnO2 and carbon and a paste of NH4Cl and ZnCl2 (electrolyte) is filled next to zinc anode.
Mercury Cell : A mercury battery is a non-rechargeable electrochemical battery. Mercury batteries use a reaction between mercuric oxide and zinc electrodes in an alkaline electrolyte.
Secondary Batteries : These cells can be recharged and can be used again and again.
Some common example of rechargeable cells are as follows :
Lead Storage Battery : It is used in automobile and invertor
When a lead storage battery is discharged then lead sulphate is formed.
Nickel-Cadmium Cell : The nickel-cadmium battery is a type of rechargeable battery. It consist of nickel oxide as cathode and metallic cadmium as anode electrodes immersed in KOH solution.
Fuel Cell : Hydrogen rich fuel and oxygen are used to generate electricity. This cell emits heat and water as by products.
In a hydrogen-oxygen fuel cell combustion of hydrogen occurs to create potential difference between the two electrodes.
