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1. R.TAMILARSAN. M. Sc., Ph.D.,
Assistant Professor of Chemistry
Chendu College of Engineering and Technology
Mudukarai-Pavinjur Road,
Zamin Endathur Village,
Madurantakam Taluk,
Kancheepuram District - 603311

2. STORAGE DEVICES

3. Battery
• Battery is a device that stores chemical energy and releases it as
electrical energy.
• i) Primary battery - not reversible, not be recharged, Ex: Dry cell,
Leclanche cell
• ii) Secondary battery - reversible, recharged, Ex: Lead-acid cell
• Iii) Fuel battery or Flow battery – Oxid-red reaction,
Ex: H2-O2 Fuel Cell
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4. Dry Cell
• A cell without fluid component is called as dry cell (1.5V).
Construction and working of Dry cell:
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5. Dry Cell
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Construction:
 Dry cell consists of zinc metal container which acts as a anode.
 A graphite rod surrounded by a mixture of powdered MnO2
and carbon acts as the cathode.
 The zinc cup is filled with a mixture of NH4Cl, ZnCl2, MnO2
and carbon powder which acts as an electrolyte.
 These reactions cannot be reversed by passing
electricity through the cell. It gives a voltage of 1.5V.
Uses:
 Dry cells are used in flash-lights, transistor radios,
calculators ect.

7. Anodic reaction
Zn(s) Zn2+(aq) + 2e─ (Oxidation)
Cathodic reaction
NH4
+(aq) + 2MnO2 (s) + 2e─ MnO(OH)- + NH3
Overall reaction
Zn(s) + 2NH4+(aq) + 2MnO2(s)
Zn2+(aq) + MnO(OH)- + NH3
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8. Lead – acid storage cell
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9. • The cell is represented as
Pb | PbSO4 || H2SO4 || PbSO4 | PbO2 | Pb
Anodic reaction:
• Pb (s) + SO4
2- PbSO4 (s) + 2e─
Cathodic reaction:
PbO2 (s) + 4H+ + SO4
2- + 2e─ PbSO4 (s) + 2H2O
Overall cell reaction during discharging:
• Pb (s) + PbO2 (s) + 2H2SO4(aq)
2PbSO4 (s) + 2H2O + Energy
• Overall cell reaction during recharging:
2PbSO4 (s) + 2H2O + Energy
Pb (s) + PbO2 (s) + 2H2SO4(aq) 9

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Fuel cell (OR) H2-O2 Cell

12. Fuel Cell Reaction
At anode
2H2 4H+ + 4e-
4H+ + 4OH 4H2O
2H2 + 4OH- 4H2O + 4e-
At cathode
O2 + 4e- 2O2-
2O2- + 2H2O 4OH–
O2 + 2H2O + 4e – 4OH –
Over all reaction
2H2 + 4 OH – 4H2O + 4e –
O2 + 2H2O + 4e – 4OH –
2H2 + O2 2H2O
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13. Advantages of fuel cell
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• Emits only Water as byproduct
• Replace battery
• Lightest element
• Less noise pollution
Disadvantage
• Explosive
• Expensive
• Difficult to convert hydrogen in liquid form.

14. Li ion Battery
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15. On Charging
LiCoO2 + C Li1-XCoO2 + CLix
On Discharging
Li1-XCoO2 + CLix LiCoO2 + C
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16. Super Capacitor
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