To maximize the benefit of the open structure, the researchers needed to use the right size ions. Too big and the ions would tend to get stuck and could damage the crystal structure when they moved in and out of the electrode. Too small and they might end up sticking to one side of the open spaces between atoms, instead of easily passing through. The right-sized ion turned out to be hydrated potassium, a much better fit compared with other hydrated ions such as sodium and lithium.
"It fits perfectly really, really nicely," said Cui. "Potassium will just zoom in and zoom out, so you can have an extremely high-power battery."
The speed of the electrode is further enhanced because the particles of electrode material that Wessell synthesized are tiny even by nanoparticle standards a mere 100 atoms across.
Those modest dimensions mean the ions don't have to travel very far into the electrode to react with active sites in a particle to charge the electrode to its maximum capacity, or to get back out during discharge.
A lot of recent research on batteries, including other work done by Cui's research group, has focused on lithium ion batteries, which have a high energy density meaning they hold a lot of charge for their size. That makes them great for portable electronics such as laptop computers.
But energy density really doesn't matter as much when you're talking about storage on the power grid. You could have a battery as big as a house since it doesn't need to be portable. Cost is a greater concern.
Some of the components in lithium ion batteries are expensive and no one knows for certain that making the batteries on a scale for use in the power grid will ever be economical.
"We decided we needed to develop a 'new ch
|Contact: Louis Bergeron|