Cells and Batteries

D.MaruthamaniD.MaruthamaniAssistant ProfessorAssistant Professor

Department of ChemistryDepartment of ChemistryPSG College of TechnologyPSG College of Technology

Coimbatore – 641 004Coimbatore – 641 004

Electrochemical power sourcesElectrochemical power sources

Cells and Batteries

Types of electrochemical cells

Cells and Batteries

Batteries

• Battery is a device consisting of a series of galvanic cells that can act as portable source of direct electric current at a constant voltage.

• Used in calculators, watches, pace makers for heart, hearing aids, computers, car engines, stand-by power supplies, emergency lighting in hospitals, electroplating, industrial traction and military and space applications.

• The size of batteries ranges from a fraction of a cubic centimetre to several cubic decimetres.

Cells and Batteries

Factors influencing the emf of batteries

According to Nernst equation at 298K

• The emf of a battery largely depends on

As the difference in the electrode potential increases the emf also increases for a given value of Q at constant temperature.

• Temperature and the concentration ratio given by reaction quotient Q.

Cells and Batteries

Leclanche cell• Invented by the French engineer George Leclanche in about 1886.• Dry cell, contains the elctrolyte in the

form of a thick paste. • Not rechargeable.

Cells and Batteries

Construction of Leclanche cell

Cells and Batteries

Working of Leclanche cell

Cells and Batteries

Limitations of Leclanche cell

• Not designed for heavy current outputs. Withdrawal about 25 to 50mA will increase the efficiency and life of battery.

• Not designed for continuous use. Intermittent usage will increase the efficiency of battery.

• When not in use for a long period, the batteries should be removed from the device and should be stored in a cool place. Otherwise, condensation can cause electrical leakage which reduces life and may destroy the battery case.

Cells and Batteries

Lead-acid battery• Invented by the French physicist Gaston Plante in the year 1893.• Rechargeable.

Cells and Batteries

Construction of lead-acid battery

Cells and Batteries

Construction of lead-acid battery (cont....)

Cells and Batteries

Working of lead-acid battery

Cells and Batteries

Working of Lead-acid battery (cont….)

Discharging reactions

Anode reaction:

Cathode reaction:

Cells and Batteries

Working of Lead-acid battery (cont….) Recharging reactions

Anode reaction:

Cathode reaction:

Cells and Batteries

Limitations of Lead acid battery

• More amounts of materials should be taken. Because, the products lead sulphate and water are poor conductors of electricity. Moreover, acid gets progressively diluted.

• Optimal charging and discharging should be done to avoid the loss of efficiency.

• Wrong polarity connection should be avoided.

• Acid concentration and proper connections should be monitored /checked frequently.

Cells and Batteries

Ni-Cd battery• Invented by the Sweden scientist Waldemar Jungner

in the year 1899.

• Rechargeable battery.

• Nickel-cadmium is the only battery type that performs well under rigorous working conditions.

Cells and Batteries

Construction of Ni-Cd batteryAnode : Cd/CdO Sheets Electrolyte : 22% KOHCathode : Nickel hydroxide with 14% Nickel foil

Cells and Batteries

Construction of Ni-Cd battery (cont...)

Cells and Batteries

Working of Ni-Cd batteryFirst charging

Cells and Batteries

Working of Ni-Cd battery (Cont…)

Discharging

Cells and Batteries

Working of Ni-Cd battery (Cont…)

Recharging

Cells and Batteries

Applications of Ni-Cd battery"Eveready" sealed nickel-cadmium batteries are

ideally suited for use in many types of battery-operated equipment.

Some of the applications are listed here:Some of the applications are listed here:Calculators Personal PagersDictating machines Digital CamerasInstruments Radio control Radios Photoflash equipmentPortable computers Tape recorders Television setsPortable hand tools and appliancesCassette players and recorders Portable communications equipment

Cells and Batteries

Fuel cells

Fuel cells are electrochemical cells in which the chemical energy of easily available fuel such as hydrogen, methane etc. is converted into electrical energy by their oxidation at suitable anodes.

Cells and Batteries

Bischoff cell

Construction:

• Fuel (here carbon) acts as anode.

• Wire gauze makes electrical connection with fuel bed.

• Oxygen electrode (set up by circulating oxygen continuously through bed of granular magnetite) acts as cathode.

• Sodium carbonate acts as electrolyte.

Cells and Batteries

Construction of Bischoff cell

Cells and Batteries

Working of Bischoff cell

Anode:

The carbon ions ( ) generated at anode react with carbonate ions present in electrolyte to form carbon dioxide.

Cells and Batteries

Working of Bischoff cell (Cont…)

Cathode:

At the cathode oxygen ionizes at the magnetite surface to form oxygen ions.

Cells and Batteries

Working of Bischoff cell (Cont…)

Since the clay support for the electrolyte is thin and porous, sodium oxide and carbon dioxide readily come into contact and in doing so react to regenerate the ionized electrolyte.

Overall reaction

Cells and Batteries

Bacon Hydrogen-Oxygen fuel cell

Cells and Batteries

Working of Hydrogen-Oxygen fuel cell• Oxygen diffuses into the cell through a porous

carbon electrode containing silver as catalyst.

• Hydrogen diffuses into the cell through a similar porous carbon electrode containing nickel or platinum as catalyst.

• The electrolyte, a warm solution of KOH, is placed between the two electrodes.

Cells and Batteries

Different Hydrogen-Oxygen fuel cells

Cells and Batteries

Different Hydrogen-Oxygen fuel cells

Cells and Batteries

Applications in automobile industry

Cells and Batteries

Applications in automobile industry

Cells and Batteries

Applications in automobile industry

Cells and Batteries

Applications in automobile industry

Cells and Batteries

Applications in automobile industry

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