How mod­ern bat­ter­ies work

The science be­hind the power sup­ply

Mac|Life - - FEATURE -

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.

Play­ing games taxes more parts of your phone, drain­ing the bat­tery quicker.

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