The electrochemical battery
It would then be another 2000 years until the first modern battery would see the light of day. When the concept of electricity was first proven by Benjamin Franklin in 1752, all the scientists had to work with was some forms of static electricity, making studying currents hard and impractical. In 1799, Italian scientist Alessandro Volta made the discovery that by placing a saltwater cloth or sheet of paper between a disc of copper and a disc of zinc to form a cell, a potential difference would be formed. This is because when in solution, the salt (NaCl) will dissociate into Na + ions and Cl - ions. As is the case with the ‘Baghdad Battery’ , copper and zinc have a different electrode potential meaning Cl - ions would migrate to the zinc disc (anode) and Na + ions would migrate to the copper disc (cathode)
Although this gave scientists more electricity to work with than they had before, with the equipment they worked with back then, the electricity was barely noticeable. Luckily, Volta came up with a very simple solution. He stacked cells on top of each other and thus in 1800 the voltaic pile was born.
Although the voltaic pile was a ground-breaking invention to carry out research on/with electricity, it had its fair share of problems. The battery only lasted one hour and had a variety of other technical issues that caused the voltage of the battery to be inconsistent and fluctuate. When using electricity in experiments it is clear how an uneven voltage might make results unreliable. Firstly, owing to the weight of all the metal discs, the saltwater would leak out of the cloths and run down the sides of the pile, causing short circuits. This problem was very easily solved by placing the pile in a horizontal box stopping any leaks. The second and slightly more complex issue was that the current would cause the release of hydrogen from water through electrolysis and the hydrogen would form little bubbles on the surface of the disc, which would in turn change the internal resistance of the battery in a process known as polarization. John Frederic Daniell set out to make a cell more reliable than Volta’s. In 1836, he designed his first prototype. Although it looked vastly different from the Pile, the Daniell c ell’s chemistry was similar. The Daniell cell is composed of two containers. One with a zinc electrode filled with zinc sulphate (ZnSO 4 ) and the other with a copper electrode filled with copper sulphate (CuSO 4 ).The two containers are connected by a salt bridge (usually a hollow tube filled with very concentrated saltwater) to allow ions to pass from one container to the other.
As with the voltaic pile, zinc and copper have different standard electrochemical potentials. Zinc on the electrode is oxidized (Zn → Zn 2+ + 2e - ) and dissolves into the solution. On the other side, copper in the copper sulphate solution is reduced (Cu 2+ + 2e - → Cu). Both of these reactions take place in three steps: atomization, ionization and hydration. The reactions between the solution and the electrodes cause a positive charge to build up at the anode and a build-up of negative charge at the cathode. To ‘ complete the circuit ’ , positive ions in the cell (Zn + , Na + ) will migrate towards the cathode through the salt bridge and sulphate ions ( SO 4 2- ) migrate to the anode. This cell is
an improvement from the voltaic pile. In the Daniell cell, the copper in solution is plated onto the copper cathode and the zinc anode is reacting and slowly dissolving into the solution. This improved cell was
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