2 research outputs found
A New Coating Method for Alleviating Surface Degradation of LiNi<sub>0.6</sub>Co<sub>0.2</sub>Mn<sub>0.2</sub>O<sub>2</sub> Cathode Material: Nanoscale Surface Treatment of Primary Particles
Structural
degradation of Ni-rich cathode materials (LiNi<sub><i>x</i></sub>M<sub>1–<i>x</i></sub>O<sub>2</sub>; M = Mn,
Co, and Al; <i>x</i> > 0.5) during cycling at both high
voltage (>4.3 V) and high temperature (>50 °C) led to the
continuous generation of microcracks in a secondary particle that
consisted of aggregated micrometer-sized primary particles. These
microcracks caused deterioration of the electrochemical properties
by disconnecting the electrical pathway between the primary particles
and creating thermal instability owing to oxygen evolution during
phase transformation. Here, we report a new concept to overcome those
problems of the Ni-rich cathode material via nanoscale surface treatment
of the primary particles. The resultant primary particles’
surfaces had a higher cobalt content and a cation-mixing phase (<i>Fm</i>3Ì…<i>m</i>) with nanoscale thickness in
the LiNi<sub>0.6</sub>Co<sub>0.2</sub>Mn<sub>0.2</sub>O<sub>2</sub> cathode, leading to mitigation of the microcracks by suppressing
the structural change from a layered to rock-salt phase. Furthermore,
the higher oxidation state of Mn<sup>4+</sup> at the surface minimized
the oxygen evolution at high temperatures. This approach resulted
in improved structural and thermal stability in the severe cycling-test
environment at 60 °C between 3.0 and 4.45 V and at elevated temperatures,
showing a rate capability that was comparable to that of the pristine
sample
Flexible High-Energy Li-Ion Batteries with Fast-Charging Capability
With the development of flexible mobile devices, flexible
Li-ion
batteries have naturally received much attention. Previously, all
reported flexible components have had shortcomings related to power
and energy performance. In this research, in order to overcome these
problems while maintaining the flexibility, honeycomb-patterned Cu
and Al materials were used as current collectors to achieve maximum
adhesion in the electrodes. In addition, to increase the energy and
power multishelled LiNi<sub>0.75</sub>Co<sub>0.11</sub>Mn<sub>0.14</sub>O<sub>2</sub> particles consisting of nanoscale V<sub>2</sub>O<sub>5</sub> and Li<sub><i>x</i></sub>V<sub>2</sub>O<sub>5</sub> coating layers and a Li<sub>δ</sub>Ni<sub>0.75–<i>z</i></sub>Co<sub>0.11</sub>Mn<sub>0.14</sub>V<sub><i>z</i></sub>O<sub>2</sub> doping layer were used as the cathode–anode
composite (denoted as PNG-AES) consisting of amorphous Si nanoparticles
(<20 nm) loaded on expanded graphite (10 wt %) and natural graphite
(85 wt %). Li-ion cells with these three elements (cathode, anode,
and current collector) exhibited excellent power and energy performance
along with stable cycling stability up to 200 cycles in an in situ
bending test