23.6 - storage and fuel cells

• Three main types of cells


  Primary, seconday, and fuel cells.
• Can primary cells be recharged?


  They are non-rechargeable and are designed to only be used once.
• How do primary cells work?


  Electrical energy is produced by oxidation and reduction at the electrodes. However, the reactions cannot be reversed. Eventually the chemicals will be used up , voltage will fall, the battery will go flat, and the cell will be discarded or recycled.
• What are primary cells often used in?


  They find use in for low-current, long storage devices such as wall clocks and smoke detectors.
• What are most primary cells based on?


  They're alkaline based on zinc and magnesium dioxide, and a potassium hydroxide alkaline electrolyte.
• Can secondary cells be recharged?


  Yes, they're rechargable.
• How does recharging of secondary cells work?


  Unlike primary cells, the cell reaction producing electrical energy can be reversed during recharging. The chemicals in the cell are then regenerated and the cell can be reused.
• Common example of secondary cells


  Lithium-ion and lithium-ion polymer cells used in our modern appliances - laptops, tablets, cameras, mobile phones.
• What do fuel cells use to create a voltage?


  Energy from the reaction of a fuel with oxygen.
• What happens to the fuel, oxygen, and electroylte in a fuel cell?


  The fuel and oxygen flow into the fuel cell and the products flow out. The electrolyte remains in the cell.
• How long can fuel cells operate for?


  They can operate continuously provided that the fuel and oxygen are supplied into the cell.
• Can fuel cells be recharged?


  They do not need to be recharged.
• What is the most common fuel used in fuel cells?


  Hydrogen.
• What products do hydrogen fuel cells produce?


  They produce no carbon dioxide during combustion, with water being the only combustion product.

  
• What electrolyte do hydrogen fuel cells have?


  An acid or alkali electrolyte.