Chemistry class 12th Secondary_Batteries_Class_12

Secondary Batteries - Class 12 Chemistry



1. Introduction
Secondary batteries are rechargeable batteries that can be recharged and reused multiple times.
Unlike primary batteries, which are discarded after one use, secondary batteries undergo
electrochemical reactions in both directions.


2. Working Principle
These batteries function based on electrochemical reactions that are reversible. During charging,
electrical energy is converted into chemical energy, and during discharging, chemical energy is
converted back into electrical energy.


3. Examples of Secondary Batteries


(a) Lead-Acid Battery
- Used in automobiles and inverters.
- Composed of lead (Pb) anode, lead dioxide (PbO2) cathode, and sulfuric acid (H2SO4) electrolyte.
- Chemical Reactions:
Discharge: Pb + PbO2 + 2H2SO4 -> 2PbSO4 + 2H2O
Charge: 2PbSO4 + 2H2O -> Pb + PbO2 + 2H2SO4


(b) Nickel-Cadmium (Ni-Cd) Battery
- Used in portable electronics and power tools.
- Composed of nickel oxide hydroxide (NiOOH) cathode and cadmium (Cd) anode.
- Chemical Reactions:
Discharge: Cd + 2NiOOH + 2H2O -> Cd(OH)2 + 2Ni(OH)2
Charge: Cd(OH)2 + 2Ni(OH)2 -> Cd + 2NiOOH + 2H2O


(c) Lithium-Ion Battery
- Common in mobile phones and laptops.
- Uses lithium cobalt oxide (LiCoO2) cathode and graphite anode.
- Chemical Reactions: