Summary AQA Alevel Chemistry Commercial Applications and Fuel cells

Commercial Applications and Fuel Cells
Fuel Cells - use energy from a reaction of a fuel with oxygen to create a voltage.
Non rechargeable cells cannot have their reactions reversed as the battery may leak or explode.
The zinc electrode which forms the casing of the battery becomes thinner as the zinc is
oxidised.
Rechargeable cells use chemical reactions which can be reversed by applying a voltage greater
than the cell voltage and this causes electrons to be pushed in the opposite direction.
Li+ + CoO2 --><--- Li+[CoO2]- (positive electrode)
Li --><-- Li+ + e- (negative electrode)
The reaction can be reversed as none of the reactants are used up or escape.
Reversible reactions work only if the product stays attached to the electrode.
If the forwards reaction gives out charge then when adding charge the reaction would be
reversed.
Water is not a good solvent for a lithium cell as the lithium would react with water.
Lithium Cells Advantages Lithium Cells Disadvantages
Reaction can be reversed Shortage of lithium
Less lithium required. Not recycled
Reduced environmental impact Leads to fires
A polymer electrolyte cannot leak or leave because it is not a liquid or paste - this is an
advantage.
Fuel Cell