Abstract
High energy density Ni-rich layered oxide cathodes
LiNi0.83Co0.12Mn0.05-xAlxO2
(x=0, 0.025, 0.05; NMC, NMCA, and NCA, respectively) are fabricated in
two different microstructural forms: (i) nanoparticles (NP) and (ii)
nanofibers (NF), to evaluate the morphology and compositional effect on
the electrochemical properties using same precursors, with the latter
fabricated by electrospinning process. Although all the cathodes exhibit
a similar crystal structure as confirmed by X-ray diffraction and Raman
spectroscopy, contrasting difference is observed in their
electrochemical properties. XRD and XPS analyses indicate a higher
amount of cationic disorder for the NP cathodes compared to their NF
counterparts. Nanofibrous Ni-rich layered oxide cathodes exhibit higher
discharge capacities at all C-rates in comparison to NP cathodes. When
cycled at 1C-rate for 100 cycles, capacity retention of 81% is observed
for NCA-NF, which is superior to all cathodes. Voltage decay as a
function of the charge-discharge cycle is found to be low (0.2 mV/cycle)
for nanofibrous cathodes compared to 1.5 mV/cycle for NP cathodes. The
good rate capability and cyclic stability of nanofibrous Ni-rich layered
oxide cathodes are attributed to a shorter pathway of
Li+ diffusion and a large proportion of the active
surface area.