Production of Materials - Comparison of Battery Cells

Production of Materials‎ > ‎4. Electrochemical Methods‎ >

Gather and present information on the structure and chemistry of a lead-acid cell and evaluate it in comparison to a button cell in terms of:

chemistry
cost and practicality
impact on society
environmental impacts

Cell type	Lead-acid cell	Button (silver oxide) cell
Appearance
Chemistry	Cell diagram Pb, PbSO₄ \| H₂SO_{4 (aq)} \| PbO₂, Pb Cathode reaction PbO_{2 (s)} + 4H⁺ + SO₄^2- +2e^– → PbSO_{4 (s)}₂O + 2H_(l) Anode reaction Pb_(s) + SO₄^2- → PbSO_{4 (s)} + 2e^– Cell voltage 2.2 V	Cell diagram Zn, ZnO \| KOH (paste) \| Ag₂O, Ag Cathode reaction Ag₂O_(s) + H₂O_(l) + 2e^– → 2Ag_(s) + 2OH^– Anode reaction Zn_(s) + 2OH^– → ZnO_(s) + H₂O + 2e^– Overall reaction Zn_(s) + Ag₂O_(s) → 2Ag_(s) + ZnO_(s) Cell voltage 1.3 V
Cost and practicality	Very large and heavy Long life Lead is a reasonably expensive metal, making the cell quite expensive Rechargeable Electrolyte must be checked regularly Level of charge easily determined	Very small and light Relatively long life Silver is an expensive metal, making the cell reasonably expensive Constant output voltage Non-rechargeable
Impact on society	Ability to recharge makes cell suitable for vehicles, where the engine can recharge the cell Allowed development of starters in vehicles Able to store solar energy when connected to solar panels Important for charge storage, such as in remote regions	Small size has allowed for miniature electric appliances Non-toxic nature has allowed for use inside the body
Environmental impacts	Do not have to be discarded/recycled after one use. Corrosive sulfuric acid can pollute the environment if spillages occur. Lead is toxic and electrodes and casings must be recycled; lead causes anaemia and affects the brain.	Have to be discarded/recycled after one use Potassium hydroxide electrolyte is caustic No highly toxic materials that will harm the environment