Modern Cells and Batteries: Modern cells and batteries based on two electrodes with different
electrode potentials. Three main times of cells- primary, secondary and fuel cells.
Primary Cells: Primary cells are non- rechargeable. Electricity is produced by oxidation and
reduction at electrodes. But reactions cannot be reversed and chemicals used up. Most are
alkaline based on zinc and manganese dioxide, and potassium hydroxide electrolyte.
Secondary Cells: Secondary cells are rechargeable and reaction can reversed. So chemicals
regenerated. Common examples are lead- acid car batteries and lithium ion in laptops and
mobile phones.
Fuel Cells: A fuel cell creates voltage by using energy from reaction of fuel with oxygen. Fuel and
oxygen flow into fuel cells and products out. Electrolyte remains in cell. Fuel cells operate
continuously if provided with continuous fuel and oxygen.
Hydrogen Fuel Cells: Hydrogen is a common fuel used, as produces no CO2 during combustion,
only water. Overall reaction- 2H2 + O2 -> 2H2O. Same mechanism as fuel cell.
Ethanol easier to store and less volatile than hydrogen. Hydrogen is more flammable.
