Interrogation of Active Battery Material Intrinsic Properties

The electrochemistry of an active material in a composite battery electrode may vary significantly depending on the selection of the type and amount of binder and conductive additives, as well as the preparation method used for the electrode.  Only a few studies on the electrochemistry of individual particles have been reported where the lithiation or delithiation of individual particles of the pure active material in the absence of any additives was conducted. These types of studies provide the ability to interrogate the intrinsic properties of an active material directly without the complications of a composite electrode.  

Here we report the electrochemistry, conductivity, and visual changes associated with the electrochemical reduction of small individual particles of electrochemically active material.   Our examination of individual small particles involves aggregates of several crystallites where the influence of grain boundaries must be considered.  In addition to quantitative electrochemistry, the particles were characterized as a function of state of charge.   For example, a nanoprobe system was utilized to determine the resistance of the particle.  Different locations within an individual particle were measured and probed the local resistance changes as a function of particle reduction.   Finally, correlation of the behavior of the individual particle was reconciled relative to bulk material electrochemical performance.  This study will help elucidate the behavior of mesoscale energy storage systems.