Electricity before the battery
Before 1800, the electricity people could study came mainly from friction machines and from the Leyden jar, a glass jar coated with metal that could store a charge and release it in a single spark. Both produced brief discharges. There was no way to get a steady current, and that limited what could be learned about it.
Galvani’s frogs
Luigi Galvani, an Italian physician and anatomist in Bologna, studied the effects of electricity on animal tissue in the 1780s. He found that a dissected frog’s leg twitched when touched by metal tools in certain circumstances, including when connected to a spark machine. He published his account in 1791 and concluded that the twitching revealed an electrical fluid in the animal itself, often called animal electricity.
Volta’s objection
Alessandro Volta, a professor at Pavia, repeated the experiments and came to a different conclusion. He argued that the electricity came from the contact between two different metals, and that the frog’s leg was acting mainly as a very sensitive detector. The two men were respectful, and neither was simply wrong. Galvani’s later work showed that muscle could twitch without two metals, which supported the idea that living tissue does produce electrical effects, and the science of nerves and muscles later confirmed that. Volta’s emphasis on metal contact was only partly right as well, since modern accounts attribute the current mostly to chemical reactions, though he reasoned correctly that different metals gave different effects.
The pile
To prove his view, Volta built a device from alternating discs of two metals, typically silver (or copper) and zinc, with a layer of cloth or cardboard soaked in brine or acid between each pair. Stacking them in a column multiplied the effect. In March 1800 he described it in a letter to Sir Joseph Banks, president of the Royal Society in London, and the letter was published in the Society’s Philosophical Transactions later that year.
The pile produced a continuous current, not a single spark. It was also a clear example of a device that turned chemical reactions into electricity. Volta designed a related arrangement called a crown of cups, in which separate vessels of liquid were linked by metal strips.
Honors followed. Volta was celebrated in Napoleonic France, and the unit of electric potential, the volt, is named for him.
Early uses and discoveries
Within weeks of the letter becoming known, William Nicholson and Anthony Carlisle used a pile to decompose water into hydrogen and oxygen, an early example of electrolysis. In 1807 Humphry Davy used a large battery of cells to isolate potassium and then sodium from their compounds, and later other elements, adding to the knowledge that went into the periodic table. Piles also made it possible to heat wires, produce arcs between carbon rods and, in time, to build the early electric telegraph and electric lighting experiments.
Problems with the first cells
Early piles were messy and weak. The brine-soaked layers dried out or leaked, and the zinc corroded quickly. A bigger problem was polarization, where bubbles of hydrogen formed on the copper and cut the current. In 1836 John Frederic Daniell introduced a cell with separate solutions that gave a steadier voltage for longer, and it became a standard for telegraph use. Later designs, such as those by William Grove and Georges Leclanché, improved output and portability, which led eventually to the dry cells found in flashlights.
Not yet rechargeable
None of these early cells could be recharged in a practical sense. Once the zinc was consumed or the chemicals changed, the cell was finished. The rechargeable lead-acid cell of 1859 was a separate step, and much later work produced lithium-ion batteries. Still, the pile established the basic pattern, two different conductors and an electrolyte, that all later batteries share.