How modern batteries work
The science behind the power supply
Though the specifics
of battery technology have changed over the years, the Lithium-ion (Li-ion) batteries used by gadget makers first appeared in the ’90s, and the principle remains the same now.
A Li-ion battery consists of two electrodes at each end (the anode and the cathode) suspended in a solution that contains lithium ions (hence the name). The ions are positively charged, and are attracted to the cathode, so they move over to it, making it positively charged in turn. This then attracts negatively charged electrons from the anode over to the cathode — and this is how it provides electricity. Electrical flow is basically the movement of electrons through a conductive system — like water running through a pipe. The trick is to make sure that the only path the electrons can take to get to the cathode is via the processor, screen, and so on, providing these elements with the power they need along the way. When you charge a battery, you attract the lithium ions to the anode, reversing the process, ready to go again.
You may know that Li-ion batteries also degrade over time. The reason for this is that some ions become stuck on the electrodes during each cycle of charging, reducing their effectiveness slightly. Consequently, over a period of time, this adds up.
Cell division
Li-ion batteries are divided into “cells,” each of which does what we’ve just described. A single product is likely to have multiple cells. This is the best way to scale them, since they can discharge together at a higher overall level of power, and be charged simultaneously, more quickly than one giant battery cell would be.