Published on June 24th, 2014 | by Chris Demorro2
Why Do Lithium-Ion Batteries Degrade When Charged?
We all know that over time, the ability of a battery to hold a charge diminishes with repeated recharged. But we haven’t known exactly why that is, especially in lithium-ion batteries, the cornerstone of the electric vehicle industry, until now that is.
Gizmodo reports that researchers seem to have figured out the physical properties of lithium-ion battery decay, and it could lead to longer lasting batteries.
The results of the findings were published in two recent studies, with Huolin Xin, a researcher at Brookhaven’s Lab for Functional Nanomaterials, co-authoring both stories. Xin sums up her findings as such;
“We discovered surprising and never-before-seen evolution and degradation patterns in two key battery materials. Contrary to large-scale observation, the lithium-ion reactions actually erode the materials non-uniformly, seizing upon intrinsic vulnerabilities in atomic structure in the same way that rust creeps unevenly across steel.
Consider the way snowflakes only form around tiny particles or bits of dirt in the air. Without an irregularity to glom onto, the crystals cannot take shape. Our nickel oxide anode only transforms into metallic nickel through nanoscale inhomogeneities or defects in the surface structure, a bit like chinks in the anode’s armor.
As the lithium ions race through the reaction layers, they cause clumping crystallization—a kind of rock-salt matrix builds up over time and begins limiting performance. We found that these structures tended to form along the lithium-ion reaction channels, which we directly visualized under the TEM. The effect was even more pronounced at higher voltages, explaining the more rapid deterioration.”
So what’s it all mean? It means that armed with this new information, battery designers can seek ways to build more robust batteries that are less concerned with fast-charging or repeated charging. That’s a pretty big deal when you think about what it means for electric vehicles.