The electrochemical battery
able to run for a lot longer than the pile and did not suffer from the polarization problem, leading to a much more stable voltage output.
In 1859, the electrical battery evolved in a way that would change the face of the future. By immersing two strips of lead rolled into a spiral and separated by a piece of rubber into a container of sulphuric acid, Gaston Plante created the world’s first rechargeable battery. The positive plate in a lead acid battery is made of lead dioxide. In lead dioxide lead has an oxidation state of +4. The reaction at the positive plate is as follows: PbO 2 + SO 4 2- + 4H + + 2e - → PbSO 4 + 2H 2 O. Pb is reduced as its oxidation state goes from 4+ to 2+. The negative plate is made of sponge lead which is a type of lead that is injected with gas in order to make it porous and increase the surface are that can be used to react. The reaction is as follows: Pb + SO 4 2- → PbSO 4 + 2e - . The lead is oxidized in this reaction as its oxidation state is going from 0 to +2. By applying a current the other way round, the chemical rection is reversed, returning to its original form, with a slight difference. One of the biggest flaws with this battery is that when the voltage is applied to the solution, water is electrolysed causing the formation of Oxygen and Hydrogen gas. This means the battery has to be constantly checked for leaks as well as the water levels. One of the other reasons why this type of battery isn’t commonly used anymore is that it was very inefficient in terms of space to energy stored. The battery could only store 80-90 Wh/dm 3 .
A trend in all of the previously mentioned designs is the leaking of materials, causing problems with the cell function. Developed by Karl Gassner in 1888, the zinc-carbon cell was the first ‘ dry cell ’ . The difference between wet cells and dry cells is that in a dry cell there are no free-flowing solutions or
electrolytes. The zinc carbon cell achieves this by trapping all of the electrolytes in a Plaster of Paris. The zinc-carbon battery is comprised of a zinc shell that acts as an anode with a graphite rod in the centre coated with manganese (IV) oxide to act as a cathode. The rest of the cell is filled with ammonium chloride and zinc chloride that has been mixed in with the Plaster of Paris to form a thick paste. When connected, the zinc at the anode oxidized in the following reaction (Zn → Zn 2+ + 2e - ). At the cathode, electrons come through the graphite electrode and reduce the ammonium to form ammonia gas (MnO 2 + NH 4 + + e - → MnO(OH) + NH
3 ). The ammonia gas would be a problem as pressure would build up in the cell causing it to blow up. However, the following reaction between zinc ions and ammonia takes place: Zn 2+ + 4NH 3 → [Zn·NH 3 ] 2+ , forming a solid and trapping the gas. Although the zinc-carbon battery cannot be recharged, it displayed several advantages over its lead acid predecessor, especially in smaller batteries. Firstly, owing to the design (especially the zinc case) and the reactions taking place, the battery had very few leaks and required very little maintenance, leading to a very long shelf life. The amount of energy stored per dm 3 was also significantly increased (120-150 Wh/dm 3 ). In 1899, Waldemar Jugner invented the world’s first alkaline battery. The alkaline battery is a battery that uses an alkaline electrolyte rather than an acidic one like its lead-acid ancestor. His design of the alkaline battery combined the rechargeability of the lead-acid battery as well as the energy density of the zinc carbon cell.
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