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Several advancements soon followed the Voltaic pile. British chemist John Frederic Daniell replaced the salt water with a solution of copper sulfate, which would be reduced into pure copper on the surface of the copper. The copper was no longer a flat plate, but a copper pot that held the solution, a zinc rod, and a porous earthenware pot separating them. The Daniell cell could generate up to 1.1 Volts without the hydrogen gas problem, a vast improvement on Volta’s short-living pile that measured only 0.8 volts. French Scientist Georges Leclanché improved on this in 1866 – he switched out the copper and copper sulfate for a carbon rod sitting in a solution containing manganese IV oxide, which would reduce to manganese (III) oxide. This upped the voltage to 1.4 Volts and found a lot of usage powering telegraphs and early telephones. This “battery,” however, was still a glass jar full of nasty chemical solutions.

The 1892 patent awarded to German Karl Gassner recognized a “dry cell” using a manganese IV oxide paste that removed as much water as possible. These dry cells could be used in any orientation without spilling, and their basic design can still be seen today in cheap, leak-prone carbon-zinc batteries that come in the standard sizes (1.5 Volt AAA, AA, C, D, and 9-volt, which are just 6 small 1.5 volt cells connected together – check out 9 volt battery hack! You’ll be surprised! Alkaline batteries are the more modern alternative, using various chemical bases that don’t eat through the metal can. They show up in our lives in all shapes and sizes imaginable.

Choosing a substance to use in a battery depends on how much electrochemical potential, or voltage, can be generated by the oxidation and reduction reactions. Reactive metals like lithium or calcium are more likely to oxidize, losing electrons to become aqueous ions. Other metals are less likely to oxidize, so they are more often found in their pure metal state (like copper, silver, or gold). A standard reduction potential shows how much voltage can be generated by an oxidation or reduction process. Metals with high, positive reduction potentials generate voltage when their ions gets reduced into metal (gold = +1.68 V, silver = +0.80 V). Metals with low, negative reduction potentials generate voltage by oxidizing to become ions (lithium = -3.05 V, calcium = -2.87 V). This is why most people are familiar with solid gold, while very few would be able to identify solid calcium. Calcium is found in nature in its ion form, usually bonded to something else. Calcium ions and carbonate ions make up limestone and marble. Silver and gold are stable as solid metal, so we use them for jewelry and coins. The Chemistry of Batteries has more information on this topic.

Batteries are energy storage devices, so they don’t really generate energy as much as they simply contain it in the chemical state of their contents. This is akin to pushing a ball up a hill – the energy used to push it up is stored in the height of the ball as gravitational potential energy. This can be turned into kinetic energy by letting the ball roll down the hill. Recharging a battery is like pushing the ball up the hill, while using a battery is like letting in roll down. These energy transfer processes are never 100% efficient though. Just like a ball being pushed up a hill will experience friction, a battery being recharged loses energy as heat. As most people can tell you, a working charger usually feels warm to the touch. Batteries also don’t hold charge indefinitely – their reactions can happen slowly even when they are not connected to a circuit. Keeping batteries disconnected from devices when not in use and using them shortly after recharging them are the best ways to boost battery efficiency! Give a try and see what happens!