Why is your phone battery dead when you just charged it this morning? An international team of scientists from ESRF, SLAC, Virginia Tech, and Purdue University completed a study that provides the first global view of lithium-ion battery failure, and what they found could supercharge the next generation of consumer electronics.
A modern lithium-ion battery is composed of solid polymers that hold particles together, carbon additives that provide electrical connection, and the active particles themselves, which hold and release the energy. Because so many electrons are interacting within this environment, state-of-charge heterogeneities are observed that can lead to over- or under-charging different regions of the battery, leading to unexpected failure.
Understanding the reasons behind these heterogeneities can lead to fast-charging, slow-discharging batteries that reshape the way we use phones, laptops, and even electric cars. But before we can get to the batteries of tomorrow, we need to understand why the batteries of today fail.
Previous studies of battery failure focused on individual particles during failure or on broad, cell-level behavior, with little consideration for the interplay of microscopic structural details and macro-level phenomena. This chemomechanical interplay is not well-understood as it involves many interrelated processes occurring over different length and time scales.
“Hard X-ray phase contrast nano-tomography showed us each particle at remarkable resolution across the full electrode thickness,” said Yang Yang, ESRF scientist and first author of the paper.
The results from this imaging method, combined with quantitative data from transmission X-ray microscopy, nanoscale hard X-ray spectromicroscopy, soft X-ray absorption spectroscopy, and transmission electron microscopy, were used to make a statistical map of chemomechanical transformation in the composite electrode. This could be used as a diagnostic method for the performance of the heterogeneous particles within a lithium-ion battery.
“Before the experiments, we didn’t know we could study these many particles at once. Imaging individual active battery particles has been the focus of this field. To make a better battery, you need to maximize the contribution from each individual particle,” says Yijin Liu, a scientist at SLAC. Nano-resolution X-ray spectromicroscopy experiments conducted at SLAC contributed key information to the project, including 3D renderings of particle cross sections.
By starting at the atomic scale and working their way up, scientists at ESRF, SLAC, Virginia Tech, and Purdue University, have generated the most complete study of battery failure to date. With a greater understanding of the way lithium-ion batteries fail, they created a diagnostic method for particle utilization and fading that can be used to develop batteries that charge faster and stay charged longer than anything we’ve seen before.
For more information on fast-charging batteries, check out the challenges of engineering them and a new charging method for electric vehicle battery packs.