posted on 2022-06-27, 18:04authored byJuliana
B. Falqueto, Adam H. Clark, Aleš Štefančič, Glen J. Smales, Carlos A. F. Vaz, Albert J. Schuler, Nerilso Bocchi, Mario El Kazzi
Li-rich
nanoparticles of Li1+xMn2–xO4 doped with Al, Co,
or Ni are successfully synthesized using a facile, fast, and efficient
microwave-assisted hydrothermal route. Synchrotron X-ray diffraction
confirms the formation of the crystalline cubic spinel phase type.
X-ray absorption spectroscopy analysis at the Co and Ni K- and L-edges
verifies that the dopants are within the Li1+xMn2–xO4 spinel
structure and are inactive during cycling in the bulk and at the surface.
Moreover, we demonstrate that nanocrystallinity and cationic doping
play an important role in improving the electrochemical performance
with respect to LiMn2O4 microparticles. They
significantly reduce the charge-transfer resistance, lower the first
cycle irreversible capacity loss to 6%, and achieve a capacity retention
between 85 and 90% after 380 cycles, with excellent Coulombic efficiency
close to 99% without compromising the specific charge at a 5C cycling
rate. Furthermore, the Mn K- and L-edges attest that after long cycling,
the Mn oxidation state in the bulk differs from that at the surface
caused by the Mn disproportion reaction; however, the cationic doping
helps mitigate the Mn dissolution with respect to the undoped Li1+xMn2–xO4 nanoparticles, as indicated by inductively coupled
plasma atomic emission spectrometry.