The Transmission Electron Microscope (TEM) at the William R. Wiley Environmental Molecular Sciences Laboratory at the Pacific Northwest National Laboratory is used to image metals, ceramics, minerals, nanostructured materials, and biological-related materials and tissues at atomic-bond-length resolution. | Photo of Pacific Northwest National Laboratory
Old batteries, like old soldiers, never seem to die; they just fade away.
A team of researchers, led by Chongmin Wang at the Pacific Northwest National Lab (PNNL), recently figured out part of that answer for one type of high-performance battery. Lithium ion batteries are used in essential everyday electronics like cell phones and laptops, and adding the element nickel to their electrodes further improves their performance. However, over time, their performance fades.
Dr. Wang and his colleagues wondered why ... and knew where to go for the tools to find out. They tapped into world-class user facilities to take a closer look at what was happening at the molecular level. Specifically, they scoped out tiny particles – nanoparticles – with the same composition. The particles were so small, about 200 nanometers in size, that it would take some 300 of them together to form a particle the size of an average speck of dust. They were created by researchers at the Argonne National Lab (ANL) using a variety of different methods – see below for why.
Researchers took some fifty images of those nanoparticles using electron microscopes at PNNL’s Environmental Molecular SciencesLaboratory and the National Center for Electron Microscopy at the Lawrence Berkeley National Laboratory. They found that the elements in the electrode (nickel, manganese and oxygen) formed rows – almost like lanes on a racetrack – between which the charged particles, the lithium ions, sped.
To the researcher’s surprise, nickel proved to be a frenemy. While nickel can improve the performance of batteries, it can also clog the course. A bit like over-excited spectators at a race, nickel atoms sometimes slip out onto the lanes taken by the lithium ions during manufacturing, sprint down them, and then clump together at the finish. There’s no way to disperse the bandits. As a consequence, the channel becomes clogged, fewer charges get through, and the battery fades.
That’s where things stand at the moment. However, since the researchers used a variety of methods to produce the nanoparticles, they could find better ways to keep nickel on the sidelines. That would lead to improved battery performance, and indeed PNNL researchers are planning on conducting more detailed experiments to see if particular manufacturing methods will create better electrodes.
There’s a metaphor in there for the labs at work: Old batteries may fade; but research can recharge and revitalize.