Herein, we report a sacrificial carbon
fiber (CF) template-assisted
synthesis of LiNi0.8Co0.15Al0.05O2 (C-NCA) by the Pechini method. An anisotropic primary particle
morphology with an interconnected microstructure is obtained, originating
from local overheating and oxygen-deficient zones induced by combustion
of the CFs during high-temperature lithiation. Moreover, the particles
assembled around the CFs demonstrated denser packing compared to the
reference bare NCA (B-NCA) synthetized in the absence of the CF template.
The anisotropic surfaces facilitate ion transport and stabilize the
structure for high voltage and temperature operation. C-NCA||Li metal
cells exhibit a reversible capacity of 106 mA h g–1 at 10 C and are able to retain 96% of their initial capacity as
the C-rate is reverted to 0.1 C. The state of health of C-NCA||graphite
full cells remains at 70% after 200 cycles at 0.33 C within 2.8–4.3
V. The results outperform the B-NCA cell, exhibiting a significant
loss over 66 cycles while delivering only 50% of its initial capacity.
The synthesis method allows for a straightforward route for tailoring
the particle size, shape, and crystallinity, enabling the development
of stable nickel-rich cathode materials, even at an upper cutoff voltage
of 4.5 V or an operating temperature of 60 °C.
We report the performance of a conversion-type magnetite-decorated
partially reduced graphene oxide (Fe3O4@PrGO)
negative electrode material in full-cell configuration with LiNi0.8Co0.15Al0.05O2 (NCA) positive
electrodes. To enable practical implementation of the conversion-type
negative electrodes in full cells, the beneficial impact of electrochemical
prelithiation on mitigating active lithium losses and improving cycle
life is shown here for the first time in the literature. The initial
Coulombic efficiency (ICE) of the full cells is improved from 70.8
to 91.2% by prelithiation of the negative electrode to 35% of its
specific delithiation capacity. The prelithiation is shown to improve
the surface passivation of the Fe3O4@PrGO electrodes,
leading to less electrolyte reduction on their surface which is prominent
from the significantly lowered accumulated Coulombic inefficiency
values, lower polarization growth, and doubled capacity retention
by the 100th cycle. The reduced surface reactions of the negative
electrode by prelithiation also aids in reducing the extent of aging
of the NCA positive electrode. Overall, the prelithiation leads to
a longer cycle life, where a retained capacity of 60.4% was achieved
for the prelithiated cells by the end of long-term cycling, which
is 3 times higher than the capacity retention of the non-prelithiated
cells. Results reported herein indicate for the first time that the
electrochemical prelithiation of the Fe3O4@PrGO
electrode is a promising approach for making conversion negative electrode
materials more applicable in lithium-ion batteries.
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