Electricity production before Volta
Before chemical cells, such as dry cells, there was only one thing we knew as a way to produce electricity. That is rubbing amber, glass, or metal.
Alessandro Volta (1745-1827) of Italy in the 18th century attempted to generate electricity chemically. He made a voltaic cell by sandwiching salt-soaked cardboard between a small copper plate and a zinc plate. He was able to create high voltages by stacking these cells vertically high.
This is humankind's first battery, the Voltaic battery. Voltaic batteries generate hydrogen gas on the surface of the zinc plate. That gases blocked the flow of current, so the efficiency was not high. This phenomenon is called 'polarization.'
After that, Daniel (1790-1845) of England prevented the generation of hydrogen gas by immersing the copper plate and the zinc plate in different containers and then connecting the containers with a salt bridge.
The Daniel battery is humankind's first battery to operate stably.
(+)pole (zinc plate): Zn → Zn2+ + 2e-
(-)pole (copper plate): Cu2+ + 2e- → Cu