Waldemar Jungner, a Swedish engineer and inventor, largely self-taught in his practical training, patents on March 11, 1899, the nickel-cadmium (NiCd) battery, the first battery to use an alkaline electrolyte (potassium hydroxide) instead of an acid electrolyte. The same year he also patents a nickel-iron (NiFe) variant, which he later abandons due to its lower performance and greater hydrogen generation compared to the cadmium version. Two years later, in 1901, Thomas Edison independently develops and patents a nickel-iron battery substantially similar to the variant Jungner had discarded, giving rise to a patent dispute between the two inventors that Edison ends up winning thanks to his greater legal and financial resources, despite Jungner's temporal priority. Jungner's battery, commercialized in Sweden from 1910 and in the USA from 1946, becomes the dominant rechargeable technology for portable and aerospace applications for much of the 20th century, until its progressive replacement by nickel-metal hydride from the 1990s onward, partly due to the environmental toxicity of cadmium.