2 research outputs found
Curious Case of Positive Current Collectors: Corrosion and Passivation at High Temperature
In
the evaluation of compatibility of different components of cell
for high-energy and extreme-conditions applications, the highly focused
are positive and negative electrodes and their interaction with electrolyte.
However, for high-temperature application, the other components are
also of significant influence and contribute toward the total health
of battery. In present study, we have investigated the behavior of
aluminum, the most common current collector for positive electrode
materials for its electrochemical and temperature stability. For electrochemical
stability, different electrolytes, organic and room temperature ionic
liquids with varying Li salts (LiTFSI, LiFSI), are investigated. The
combination of electrochemical and spectroscopic investigations reflects
the varying mechanism of passivation at room and high temperature,
as different compositions of decomposed complexes are found at the
surface of metals
Auger Electrons as Probes for Composite Micro- and Nanostructured Materials: Application to Solid Electrolyte Interphases in Graphite and Silicon-Graphite Electrodes
In
this study, Auger electron spectroscopy (AES) combined with
ion sputtering depth profiling, X-ray photoelectron spectroscopy (XPS),
and scanning electron microscopy (SEM) have been used in a complementary
fashion to examine chemical and microstructural changes in graphite
(Gr) and silicon/graphite (Si/Gr) blends contained in the negative
electrodes of lithium-ion cells. We demonstrate how AES depth profiling
can be used to characterize morphology of the solid electrolyte interphase
(SEI) deposits in such heterogeneous media, complementing well-established
methods, such as XPS and SEM. In this way we demonstrate that the
SEI does not consist of uniformly thick layers on the graphite and
silicon; the thickness of the SEI layers in cycle life aged electrodes
follows an exponential distribution with a mean of ca. 13 nm for the
graphite and ca. 20–25 nm for the silicon nanoparticles (with
a crystalline core of 50–70 nm in diameter). A “sticky-sphere”
model, in which Si nanoparticles are covered with a layer of polymer
binder (that is replaced by the SEI during cycling) of variable thickness,
is introduced to account for the features observed