This document discusses different types of storage devices including batteries, dry cells, lead-acid storage cells, fuel cells, lithium-ion batteries, and super capacitors. It provides details on the construction and chemical reactions that occur in dry cells and lead-acid storage cells during charging and discharging. Fuel cells are described as using hydrogen and oxygen reactions to produce water and electricity with no emissions besides water. Lithium-ion batteries involve lithium ions moving between the anode and cathode during charging and discharging. Super capacitors store electrical charge on the surface of high surface area electrodes but do not rely on chemical reactions.

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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