BET­TER BATTERIES

Cosmos - - Cosmos Science Club -

When it comes to batteries, lithium-ion is king. They’re light­weight and very energy dense, mean­ing they pack more power per weight than other batteries.

But they’re also prone to catch­ing fire if dam­aged. And if ev­ery car went elec­tric or hy­brid, there wouldn’t be enough lithium to go around. So re­searchers are look­ing at ways to make them safer and re­place lithium with more plen­ti­ful, cheaper me­tals.

Dif­fer­ent lithium-ion batteries have dif­fer­ent com­pounds at the an­ode and cath­ode. Briefly, the lithium-ion bat­tery you might find in your smart­phone com­prises a pos­i­tive elec­trode (an­ode) made of lithium cobalt ox­ide and a neg­a­tive elec­trode (cath­ode) of car­bon bathed in elec­trolyte. The elec­trodes are sep­a­rated by a thin plas­tic mem­brane that se­lec­tively lets lithium ions through.

As the bat­tery charges, lithium ions move from the an­ode through the mem­brane to the cath­ode. As it dis­charges, the ions move back to the an­ode. Elec­trons, blocked by the mem­brane, travel to the an­ode through an ex­ter­nal wire to pro­duce elec­tric­ity. Sodium is a con­tender to re­place lithium, but be­cause sodium ions are larger and heav­ier, the batteries aren’t as energy-dense. And while that might rule them out for smart­phones, they’re ideal for jobs such as stor­ing so­lar energy. Cal­cium, mag­ne­sium, alu­minium and potas­sium are also in the run­ning, with each at vary­ing de­grees of re­search, pro­to­typ­ing and com­mer­cial­i­sa­tion.

What about safety? Sam­sung’s no­to­ri­ously faulty Note 7 batteries caught fire when the sep­a­ra­tor mem­brane wore thin or tore and the elec­trodes touched. This short-cir­cuited the bat­tery, ig­nit­ing the flammable elec­trolyte. To this end, ma­te­ri­als sci­en­tists are ex­plor­ing non-flammable, solid elec­trolytes.

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