that has nickel and cadmium electrodes in a potassium hydroxide solution; the first battery to use an alkaline electrolyte. It was commercialized in Sweden in 1910 and reached the United States in 1946. The first models were robust and had significantly better energy density than lead-acid batteries, but were much more expensive. 20th century: new technologies and ubiquity Nickel-iron Waldemar Jungner patented a nickel–iron battery in 1899, the same year as his Ni-Cad battery patent, but found it to be inferior to its cadmium counterpart and, as a consequence, never bothered developing it. It produced a lot more hydrogen gas when being charged, meaning it could not be sealed, and the charging process was less efficient (it was, however, cheaper). Seeing a way to make a profit in the already competitive lead-acid battery market, Thomas Edison worked in the 1890s on developing an alkaline based battery that he could get a patent on. Edison thought that if he produced a lightweight and durable battery electric cars would become the standard, with his firm as its main battery vendor. After many experiments, and probably borrowing from Jungner's design, he patented an alkaline based nickel–iron battery in 1901. However, customers found his first model of the alkaline nickel–iron battery to be prone to leakage leading to short battery life, and it did not outperform the lead-acid cell by much either. Although Edison was able to produce a more reliable and powerful model seven years later, by this time the inexpensive and reliable Model T Ford had made gasoline engine cars the standard. Nevertheless, Edison's battery achieved great success in other applications such as electric and diesel-electric rail vehicles, providing backup power for railroad crossing signals, or to provide power for the lamps used in mines. Common alkaline batteries Until the late 1950s, the zinc–carbon battery continued to be a popular primary cell battery, but its relatively low battery life hampered sales. The Canadian engineer Lewis Urry, working for the Union Carbide, first at the National Carbon Co. in Ontario and, by 1955, at the National Carbon Company Parma Research Laboratory in Cleveland, Ohio, was tasked with finding a way to extend the life of zinc-carbon batteries. Building on earlier work by Edison, Urry decided instead that alkaline batteries held more promise. Until then, longer-lasting alkaline batteries were unfeasibly expensive. Urry's battery consists of a manganese dioxide cathode and a powdered zinc anode