One of the biggest problems with batteries is the time it takes to recharge.
Now, Ibrahim Abou Hamad of Mississippi State University and his team have unveiled an entirely new technique for charging lithium-ion batteries that could lead to exponential improvements in recharge times.
The end of a lithium battery, the anode, is made up of a graphite electrode, that is, a stack of graphene sheets, bathed in an electrolyte of propylene carbonate and ethylene carbonate molecules through which the gases are diffused. lithium ion and hexafluorophosphate. During charging, an electric field pushes the lithium ions into the graphene sheets, where they have to cross a potential barrier to become embedded and stored, a process called intercalation.
The Mississippi team has studied the motion of these ions and molecules by creating a computer model of the forces acting on them. His model consists of 160 carbon atoms arranged in four sheets of graphene, 69 molecules of propylene carbonate and 87 of ethylene carbonate that form a liquid electrolyte and, finally, two hexafluorophosphate ions and 10 lithium ions. They then apply an electric field through this system and see what happens.
It turns out that while the electric field pushes the lithium ions toward the graphene, the speed limiting step is the intercalation process; the speed at which lithium ions can cross the potential barrier and enter the interior of graphene.
What Hamad and his colleagues have discovered is a relatively simple way to overcome this hurdle. The trick is to superimpose an oscillating electric field on the charge field. This helps the lithium ions jump over the barrier.
Source: Technology Review Blogs