V. Focused Fundamental Research - EERE - U.S. Department of ...

V.F.2 Novel In Situ Diagnostics Tools for Li-ion Battery Electrodes (LBNL)
Jordi Cabana, Robert Kostecki
Lawrence Berkeley National Laboratory
1 Cyclotron Rd. MS62R0203
Berkeley, CA 94720-8168
e-mail: jcabana@lbl.gov
Phone: (+1) 510-486-7097
Fax: (+1) 510-486-8097
Start Date: September 2009
Projected End Date: September 2011
Objectives
· Develop synchrotron-based Transmission X-ray
Microscopy (TXM) and X-ray Raman Spectroscopy
(XRS) for the production of unprecedented insight
into Li-ion battery electrode operation.
· Develop setups that allow the collection of data
during the electrochemical reaction.
Technical Barriers
Better understanding of the fundamental processes
that occur in Li-ion batteries at different levels is essential
for progress toward better performance. There is a need for
new diagnostics techniques with high sensitivity and that
cover wide time and dimension scales to probe phenomena
at surfaces and interfaces, and the evolution of the phase
transitions and boundaries upon electrode operation. Given
the importance of kinetics and transient phenomena that
occur in batteries, the development of these new
techniques must run concurrent to the development of
setups that enable the performance of experiments in real
time.
Technical Targets
· Understand impact of materials and electrode design
on performance and the underlying mechanisms of
reaction.
· Develop synchrotron-based tools for the study of
fundamental processes in battery materials.
· Streamline the use of these tools to answer questions
that span from fundamental to close-to-application
problems, with potential impact in other DOE
programs such as BATT or ABR.
· Obtain 2D and 3D maps with chemical resolution of
battery electrodes reacting through intercalation and
conversion mechanisms.
· Reveal the nature of chemical bonding between Li
and host lattice in intercalation materials.
Accomplishments
· 2D and 3D Fe K edge XANES tomography images of
partially delithiated LiFePO 4 have been collected.
· XRS data on graphite and its lithiated compounds has
revealed the changes in electronic structure and
bonding occurring in the material.
· In operando setups for XRS and TXM have been
designed and demonstrated.
Introduction
In order to fulfill the energy density and life
requirements for batteries in emerging applications such as
transportation or grid storage, new electrode materials
have to be developed and the performance of existing
materials maximized. Because Li-extraction/insertion is a
diffusion-controlled process that depends on both electron
and ion conduction, the design of architectures that
optimize these parameters is critical to achieve ultimate
performance. Fundamental understanding of how the
number of points of contact for transport of electrons from
the current collector and ions from the electrolyte into the
active material particles affects the utilization of the
material is needed to approach these limits. Nevertheless,
this picture still ignores the fact that Li extraction in a
variety of candidate materials is further complicated by the
fact that it involves multiple consecutive (even
simultaneous) phases, in which the movement of interfaces
is key to the progress of the reaction. Therefore, insight
into how individual particles electrochemically transform
depending on conditions such as particle size/shape,
carbon coating or rate at which the material is operated,
could provide vital information that could be integrated
into the process of electrode design to result in
architectures with close-to-theoretical utilization.
On the other hand, diffusion within the active material
particle will determine how large this particle can be to
perform satisfactorily at desired rates of operation. This
diffusion is determined by the interaction of the charge
carrier with its environment. Therefore, understanding of
the nature of chemical bonding between ions and the
lattice can provide valuable information about the
bottlenecks that exist for their mobility. Removing these
barriers through materials design could enable the use of
larger particles which, in turn, increase the density of the
Energy Storage R &D 666 FY 2011 Annual Progress Report