An international team of researchers has developed a proof of concept technique for precisely tracking the movement of lithium ions moving through a polymer electrolyte within batteries.
Researchers used X-rays to determine the velocity and concentration of ions within a battery, then compared those results to theoretical models to determine the ion transport number, a fraction of electric current carried by ions in an electrolyte.
The team’s calculations put the transport number at around 0.2, which differs from those derived by other methods due to the sensitivity of this new way of measuring ion movement, the researchers said.
The true value transport number has been the subject of some debate among scientists for years, according to Michael Toney, professor at the University of Colorado Boulder and an author on the paper.
Results of the tests were published in the peer reviewed journal Energy and Environmental Science.
The team included scientists from the US institutes Argonne National Laboratory and University of Colorado and Paderborn University in Germany.
The researchers measured the reactions in real time using the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility at DOE’s Argonne National Laboratory,
The team used ultra-bright X-rays to measure the velocity of the ions moving through the battery, and to simultaneously measure the concentration of ions within the electrolyte, while a model battery discharged.
Professor Michael Toney from the University of Colorado, said: “I expect to apply these kinds of methods to a broad range of battery materials over the next few years. In addition, I’d like to apply these methodologies to bio- and other polymers to study transport of ions in these systems.
“I see that there is the prospect to make tremendous progress in the next decade in terms of understanding the microscopics of ion transport and, from this, designing better electrolytes.
“This work helps to validate some of the simulations that are used to model batteries. Our work provides confidence in these models and their fidelity. This is the short-term impact. In the longer term, this work will help to guide the development of better electrolytes for batteries and other technologies.”
The next step is to analyse more complex polymers and other materials, and eventually into liquid electrolytes— these could include ions from other types of material, like calcium and zinc.