Lithium-ion battery pack for 2014 Chevrolet Spark EV electric carEnlarge Photo
Existing lithium-ion batteries rely on the movement of lithium ions between the anode and cathode--and back--as the battery charges and discharges.
It's one of the best options we have for powering electric vehicles (and most consumer electronic devices, for that matter) but there's still room for improvement.
Researchers at Stanford University have published a report in the Nature Nanotechnology journal detailing the creation of a pure lithium anode, potentially boosting battery efficiency by a large margin over today's units.
According to Phys.org, a pure lithium anode is considered the 'Holy Grail' of battery design, returning the usual improved-battery benefits: higher energy density, lighter weight and more power.
In an existing lithium-ion battery, the anode is typically made of graphite or silicon. These are largely used for their stability, rather than their efficiency.
A lithium anode would be ideal, but it's also unstable--the lithium expands during charging, causing cracks and fissures in the anode, lithium ions escape, and battery life is reduced. Not only that, but a lithium anode chemically reacts with the electrolyte, further reducing its life. And the reaction also causes heat, potentially leading to fires.
To fix these issues, Stanford's researchers have turned to carbon nanospheres. Arranged in a honeycomb structure, the nanospheres form a protective layer over the lithium, remains stable during charging and discharging, and prevents damaging expansion of the lithium as the battery charges.
Yi Cui, a professor of Material Science and Engineering, says the carbon layer is the ideal level of stability for protecting the lithium layer, and withstanding its expansion.
It also has high coulombic efficiency--the ratio of lithium extracted from the anode during use to the amount that can be put back during charging--and the team believes that with just a little more work on electrolytes and some additional engineering, the new anode could be ready for the next generation of lithium batteries.
We've heard that before, of course----battery research doesn't always pan out. But as ever, we'll be watching Stanford's progress with interest.
[Hat tip: Aaron Bragman]