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

V.E Cell Analysis, Modeling, and Fabrication (DOE)
Duong – DOE
V.E Cell Analysis, Modeling, and Fabrication
V.E.1 Electrode Fabrication and Failure Analysis (LBNL)
Vincent Battaglia (Principal Investigator)
Lawrence Berkeley Nationl Laboratory
1 Cyclotron Road
M.S.70R0108B
Berkeley, CA 94720
Phone: (510) 486-7172; Fax: (510) 486-4260
E-mail: vsbattaglia@lbl.gov
Start Date: October 1, 2009
Projected End Date: September 31, 2013
Objectives
· Develop fundamental understanding of the effect of
electrode fabrication procedures on cell performance.
· Develop techniques for evaluating cell failure.
· Provide full- and half-cell evaluations of materials
with the potential to improve energy density or life
over the baseline.
Technical Barriers
Electrode performance as a function of electrode
fabrication is poorly understood. Measuring the cycle life
of a new material can be confounded with poor electrode
fabrication.
All Li-ion cells fail with time. Much of the failure is a
result of side reactions in the anode and/or the cathode;
although, the rate of cell failure is only a fraction of the
rate of the side reactions. Understanding the underlying
source of cell failure is critical to solving the problem.
For FY2011, the BATT Program decided to put more
emphasis on higher voltage systems as this is a path to
higher energy density cells. The Program selected the
high-voltage LiNi 1/2 Mn 3/2 O 4 spinel material as a baseline
for the studies. Understanding how this material fails
against different counter electrodes may provide clues to
its failure mechanism/s.
Technical Targets
· Develop electrode fabrication capabilities that allow
for the cycling of materials to > 1000 cycles.
· Assess the rate of capacity fade of LiNi 1/2 Mn 3/2 O 4
against the PHEV and EV life targets.
Accomplishments
· Measured the rate of side reactions on graphite and
NCM when each is cycled against Li and when cycled
against each other.
· Determined the upper cut-off voltage limit when
cycling LiNi 1/2 Mn 3/2 O 4 against Li and against
graphite.
· Measured the rate of capacity fade of the
LiNi 1/2 Mn 3/2 O 4 cell and showed that the side reactions
are 4 times greater than the rate of capacity fade.
· Measured the amount of dissolution of fresh
electrodes of LiNi 1/2 Mn 3/2 O 4 in electrolyte.
Introduction
Cell manufacturing in the US is improving. Cells are
now seen to last 1000 cycles, but not 5000 cycles as is
required for PHEVs. This group’s cell manufacturing
capabilities have kept pace. Our goal is to test good
materials in cells and identify main sources of fade, in the
face of limited capcity fade. Since most cells appear to die
as a result of deleterious side reactions, we will pay special
attention to the rate of these reactions and attempt to
identify those that are benign and those that contribute to
failure. We will develop new electrochemical methods
where necessary.
If the challenging energy density targets of EVs and
PHEVs are to be realized, materials capable of cycling
larger quatities of lithium and at higher voltages are
required. To begin developing high-voltage electrolytes,
high-voltage cathodes are required. LiNi 1/2 Mn 3/2 O 4
intercalates lithium with a flat potential at 4.7 V. This
material will be evaluated for its performance and
cycleability against different counter electrodes.
Approach
The BATT Program has identified the high-voltage
Ni-spinel material as part of a system of interest. Our role
is to identify a baseline cell chemistry. This chemistry
must have reasonably good cycleability. Once established,
our role is to quatify the sources of fade, whether it is
power or energy. We accomplish this through particle
analysis, electrode analysis, half-cell analysis, and full cell
Energy Storage R &D 628 FY 2011 Annual Progress Report