  Li-ion battery (LIB) research has continuing importance for the entire range
of applications from consumer products to vehicle electrification and grid
stabilization. In many cases, standard electrochemical methods only provide an
overall voltage or specific capacity, giving an inadequate description of
parallel redox processes or chemical gradients at the particle and pack level.
X-ray absorption fine structure (XAFS) is frequently used to augment bulk
electrochemical data, as it provides element-specific changes in oxidation
state and local atomic structure. Such microscopic descriptors are crucial for
elucidating charge transfer and structural changes associated with bonding or
site mixing, two key factors in evaluating state of charge and modes of cell
failure. However, the impact of XAFS on LIB research has been significantly
constrained by a logistical barrier: contemporary XAFS work is performed almost
exclusively at synchrotron x-ray light sources, where beamtime is infrequent
and experiment time-frames are limited. Here we show that modern laboratory
based XAFS can not only be applied to, e.g., characterization of ex situ LIB
electrode materials, but can also be used for operando studies at
industrially-relevant charging rates in a standard pouch cell preparation. Such
capability enables accelerated discovery of new materials and improved
operation modes for LIBs.

Applied Physics