Storage Cells

• Storage cells, often called batteries, are electrochemical cells that convert stored chemical energy into electrical energy. They consist of two electrodes, an electrolyte, and a separator.

• The two types of storage cells are primary (non-rechargeable) and secondary (rechargeable). An example of a primary cell is the alkaline cell, while examples of secondary cells include lead-acid batteries and lithium-ion batteries.

• In these cells, oxidation-reduction (redox) reactions occur, which involve a transfer of electrons from the substance that gets oxidised (loses electrons) to the substance that gets reduced (gains electrons).

• Each cell has a positive terminal (cathode) and a negative terminal (anode). Oxidation takes place at the anode, and reduction takes place at the cathode.

• Lithium-ion batteries are widely used in portable devices because of their high energy density, long lifespan, and lack of memory effect. They work on the principle of movement of lithium ions from the negative electrode to the positive when discharging, and vice versa when charging.

• Lead-acid batteries, commonly used in cars, rely on an acidic electrolyte. When the battery is discharging, the lead anode is oxidised to lead(II) ions, and the lead dioxide cathode is reduced to lead(II) ions. During charging, these reactions are reversed.

• The efficiency and lifetime of a battery can be affected by factors such as temperature, rate of discharge, and depth of discharge. Overcharging, especially of secondary cells, can also damage the battery.

• The ‘voltage’ or ‘potential difference’ of a cell is related to the energy change in the redox reactions occurring within the cell. Electrochemical cells can be linked together in series to increase the total voltage.

• Consideration of environmental concerns has led to ongoing research into improved battery technologies, like developing environmentally-friendly methods for disposal and recycling, and creating batteries with better performance and reduced reliance on scarce resources.

• Recent advancements include the development of fuel cells, such as the hydrogen-oxygen fuel cell, which convert the energy from the reaction of a fuel with oxygen directly into electrical energy, significantly improving efficiency compared to traditional combustion methods.