Invited Paper TF-ThA3
Mapping Li-ion Diffusion on the Nanoscale in Thin Film Battery Materials

Thursday, October 21, 2010, 2:40 pm, Room Ruidoso

The electrochemical energy storage systems based on Li-based insertion and reconstitution chemistries are a vital aspect of energy technologies. Despite the wealth of device-level and atomistic studies, little is known on the mesoscopic mechanisms of ion diffusion and electronic transport on the level of grain clusters, individual grains, and extended defects.

The development of the capability for probing ion transport on the nanometer scale is a key to deciphering complex interplay between structure, functionality, and performance in these systems. Here we demonstrate how Scanning Probe Microscopy can be utilized to measure Li-ion mobility based on the strong strain-bias coupling in the system when local Li concentrations are changed by electrical fields. The imaging capability, as well as time- and voltage spectroscopies analogous to traditional current based electrochemical characterization methods are developed. The reversible intercalation of Li and mapping electrochemical activity in LiCoO2 is demonstrated, illustrating higher Li diffusivity at non-basal planes and grain boundaries. In Si-anode device structure, the direct mapping of Li diffusion at extended defects and evolution of Li-activity with charge state is explored. The electrical field-dependence of Li mobility is studied to determine the critical bias required for the onset of electrochemical transformation, potentially allowing reaction and diffusion processes in the battery system to be separated at each location. The Scanning Probe Microscopy measurements are compared with classical characterization methods such as cyclic voltammetry and electrochemical impedance spectroscopy. The prospects of Scanning Probe Microscopy for battery characterization are discussed.

This material is based upon work supported as part of the Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number ERKCC61. Part of worked is performed as a user proposal in the Center for Nanophase Materials Sciences at ORNL.