A collaborative study led by Cornell University in Ithaca, NY, used X-ray nanoimaging to obtain an unprecedented view of solid electrolytes, revealing previously undetected crystal defects and dislocations.
For half a century, materials scientists have investigated the effects of small defects in metals. The evolution of imaging tools has created an opportunity to investigate other materials, especially similar phenomena used in energy storage.
The team uses synchrotron radiation to reveal atomic-scale defects in battery material that were not found by traditional approaches such as electron microscopy. They are particularly interested in solid electrolytes as they have the potential to replace liquid and polymer electrolytes in lithium-ion batteries. One of the main drawbacks of liquid electrolytes is the tendency for spike-like dendritic projections to form between the anode and cathode, causing the battery to short-circuit or, worse, to explode.
While solid electrolytes have the advantage of being nonflammable, they have their own challenges. They do not conduct lithium ions as strongly or quickly as liquids, and it can be difficult to maintain contact between the anode and cathode. The solid electrolyte should also be very thin. Otherwise, the battery will be bulky and the capacity increase will be disabled.
What makes solid electrolytes feasible? Small defects can promote the diffusion of ions, which are known to occur in metals. This allows the ions to move faster. Like metal, defects are better at preventing damage.
The Cornell University team then partnered with Virginia Tech researchers who synthesized lithium lanthanum zirconium oxide (LLZO) with a garnet crystal structure to add different concentrations of aluminum in a process called doping.
Using the advanced photon sources of the US Department of Energy’s Argonne National Laboratory, they adopted a technique called Bragg Coherent Diffraction Imaging. Of LLZO. The electrolyte is made up of these millions of particles. The beam created a 3D image and finally revealed the morphology and atomic displacement of the material.
Initially, the electrolyte was supposed to be a perfect crystal, but the team discovered defects such as dislocations and grain boundaries that had never been reported before. Without 3D imaging, which is very sensitive to defects, the dislocation density is so low that it is probably impossible to see these dislocations.
Researchers are currently planning to conduct research to measure how defects affect the performance of actual battery solid electrolytes.
“I know exactly what I’m looking for, and I want to find these flaws and look them up when operating the battery,” said group leader Andrej Singer. “It’s still far from there, but it may be the beginning of a new development where these defects can be deliberately designed to make better energy storage materials.”
https://www.techbriefs.com/component/content/article/1537-tb/insiders/pm/stories/39357-nanoscale-defects-could-boost-energy-storage-materials?Itemid=690 Nanoscale defects can enhance energy storage materials