Sammendrag
This study compares the physico- and electro- chemical properties of
LiNi0.8Mn0.10Co0.1O2
(NMC811) and LiNi0.83Mn0.06Co0.09Al0.1O2
(NMCA) prepared by an
oxalic acid co-precipitation. Deposition of a SiO2
surface coating was attempted via
reaction of the powder with an amino silane prior to the final heat treatment. It was found
that either the presence of small amounts of Al3+, or the compositional gradient resulting
from a two step co-precipitation, caused increased crystal growth of the NMCA in
comparison to NMC811. This led to improved cyclability in LP40 electrolyte. However,
the SiO2
coating appeared incomplete and negatively impacted performance. Crystal
cleavage preferably on the {001} planes was observed after 100 charge-discharge cycles,
Downloaded from https://www.cambridge.org/core. SINTEF, on 13 Jun 2020 at 10:36:09, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/adv.2020.90
with consequent cathode electrolyte interphase formation in the crystal cracks. This is
believed to cause capacity decay via lithium loss, and increased charge transfer
resistance. An FEC based electrolyte improved the cyclability in all cases and even under
extreme conditions (45°C and upper cycling potential of 4.5 V) NMCA showed a
capacity retention of 85% after 100 cycles
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