Caging the Li-ion

THE digital devices that rule modern life may be advancing at breakneck speed, but the rechargeable batteries that power them are making slower progress. The lithium-ion (Li-ion) batteries found in everything from smartphones and laptops to Teslas and Boeing 787s have been on sale since 1991, their performance gradually improving. But to make the kinds of gains seen in the devices they energise, they need more of the one thing they have surprisingly little of: lithium.

Like other batteries, Li-ions consist of two electrodes (an anode and a cathode) separated by an electrolyte. In a typical Li-ion cell, the anode is made of graphite, the cathode is lithium cobalt oxide, and the electrolyte is a solution of lithium salts and organic solvents. Charging the battery drives positively charged lithium ions in the electrolyte to the negatively charged anode, where they accumulate. When the battery is in use, electrons flow from the anode into a device’s circuit and re-enter the battery via the cathode.