NANOCRYSTALLINE ELECTRODES FOR HIGH POWER AND ENERGY STORAGE DEVICES
Philip Jones, Santhanam Raman, and Rambabu Bobba
Solid State Ionics Laboratory, Department of Physics
Southern University and A&M College
Baton Rouge, Louisiana-70813 [[email protected]]
In an effort to develop high voltage and high capacity cathodes for energy storage devices
such as asymmetric supercapacitors, and Li ion batteries, we have developed novel processing routes
to obtain variety of nanostructured layered and spinel type oxides with unique particle characteristics
and controlled composition to reap the maximum benefits for enhancing energy and power densities.
In particular, to fully understand the electrode-electrolyte interfacial reactions and phase
transformations that accompany charge transfer and a fundamental knowledge of how nanoscale
surface composition, structure, and defects affect these processes, advanced spectro-electrochemical
measurements such as HR-TEM, EXAFS and XANES were made. Our results show that the particle
size down to < 10 nm along with distributed porosity (synthesized via our proprietary low temperature
protocol) yields much enhanced electrode-active characteristics of positive electrode materials and
their nanodot derivatives of impregnated complexes into mesoporous carbon structures.
In this presentation, we aim to show an overview of the porosity and particle size correlations
with that of device performance based on layered (LiCo1/3Ni1/3Mn1/3O2, Li1+xNi1-y-zCoyMnzO2,
xLi2MnO3
3
(1-x)LiMO2)
and
spinel
type
(LiMn2O4,
LiNi0.5Mn1.5O4,
Li2NiTiO4,
Li2CrTiO4,Li4Ti5O12) nano scale electrodes , as positive (cathode) and negative (anode) electrodes as
well are prepared in our laboratory using sol gel, co-precipitation, hydrothermal, solvothermal and
ionothermal methods. The results showed that the use of nanosized materials was advantageous for
obtaining a better rate capability where as the use of microsized materials was beneficial for better
capacity retention during extended cycling at high C-rates. In order to ensure good cell performance,
nanometric particles must meet another requirement; thus they should contain few surface or bulk
defects (i.e., they should be highly crystalline). Figure 1 a, b, c, and d show Powder XRD (b) SEM (c)
TEM and (d) EDX of LiCrTiO4 prepared by sonochemical method
Figure 1 e show the galvanostatic charge/discharge curves of the LiCrTiO4/AC hybrid supercapacitor at
different discharge current densities in 1M LiPF6 in EC/DMC electrolyte between 1.0 and 3.0 V vs. Li/Li+
Acknowledgemet: This work is supported by U.S-DOD-ARO-Advanced Power and Electrochemistry