You probably know the feeling. Your phone utters
its final plaintive "bleep" and cuts out in the middle of your call. In that moment, you may feel more
like throwing your battery across the room than singing its praises, but batteries are a triumph of science. They allow smartphones
and other technologies to exist without anchoring us
to an infernal tangle of power cables. Yet even the best batteries
will diminish daily, slowly losing capacity
until they finally die. So why does this happen, and how do our batteries even store
so much charge in the first place? It all started in the 1780s
with two Italian scientists, Luigi Galvani and Alessandro Volta, and a frog. Legend has it that as Galvani
was studying a frog's leg, he brushed a metal instrument
up against one of its nerves, making the leg muscles jerk. Galvani called this animal electricity, believing that a type of electricity
was stored in the very stuff of life. But Volta disagreed, arguing that it was the metal itself
that made the leg twitch. The debate was eventually settled
with Volta's groundbreaking experiment. He tested his idea with a stack
of alternating layers of zinc and copper, separated by paper or cloth
soaked in a salt water solution. What happened in Volta's cell is something
chemists now call oxidation and reduction. The zinc oxidizes,
which means it loses electrons, which are, in turn, gained by the ions in
the water in a process called reduction, producing hydrogen gas. Volta would have been shocked
to learn that last bit. He thought the reaction
was happening in the copper, rather than the solution. None the less,
we honor Volta's discovery today by naming our standard unit
of electric potential "the volt." This oxidation-reduction cycle creates
a flow of electrons between two substances and if you hook a lightbulb
or vacuum cleaner up between the two, you'll give it power. Since the 1700s, scientists have improved
on Volta's design. They've replaced the chemical solution
with dry cells filled with chemical paste, but the principle is the same. A metal oxidizes,
sending electrons to do some work before they are regained
by a substance being reduced. But any battery has a finite
supply of metal, and once most of it has oxidized,
the battery dies. So rechargeable batteries give us
a temporary solution to this problem by making the oxidation-reduction
process reversible. Electrons can flow back
in the opposite direction with the application of electricity. Plugging in a charger draws
the electricity from a wall outlet that drives the reaction
to regenerate the metal, making more electrons available
for oxidation the next time you need them. But even rechargeable batteries
don't last forever. Over time, the repetition of this process
causes imperfections and irregularities in the metal's surface
that prevent it from oxidizing properly. The electrons are no longer available
to flow through a circuit and the battery dies. Some everyday rechargeable batteries will die after only hundreds
of discharge-recharge cycles, while newer, advanced batteries
can survive and function for thousands. Batteries of the future
may be light, thin sheets that operate on the principles
of quantum physics and last for hundreds
of thousands of charge cycles. But until scientists find a way
to take advantage of motion to recharge your cell battery,
like cars do, or fit solar panels
somewhere on your device, plugging your charger into the wall, rather than expending
one battery to charge another is your best bet to forestall
that fatal "bleep."
