Thomas Alva Edison patented his most complex invention since the quadruplex telegraph in 1874. It was the rechargeable cadmium-copper battery. When the battery discharges, the cadmium becomes cadmium oxide and the cupric oxide becomes copper. When recharging, the reverse occurs. Even the water in the electrolyte decomposes and then regenerates. There is so little evaporation that the cell doesn’t even need a refill cap, unlike its competitors on the market at the time. It is a cutting-edge battery that pays homage to Volta’s battery of a century earlier.
