Ni2+/Ni4+ and O2–/O
n
2– redoxs endow the Li-rich
layered oxide of Li1.2Mn0.6Ni0.2O2 (LMNO) with a considerable specific capacity and higher voltage.
However, during the repeated de-/lithiation, the constant structure
degradation initiated from transition metal ion dissolvement and oxygen
escape leads to rapid capacity decay, which severely hinders the commercial
application of LMNO. Herein, Nb2O5 and LiNbO3 are fabricated on the outside of the LMNO substrate. With
the appropriate ion radius, a small amount of Nb5+ enters
the substrate, which could enlarge the crystal spacing and facilitate
the fast Li+ transfer and, more importantly, change the
valence state of Mn and induce the formation a Fd3̅m transition phase on the interface between
the coating layer and the interior LMNO. Density functional theory
(DFT) calculation has proven that the transition phase could build
double-way chemical bonds both inside and outside, and the LiNbO3 coated LMNO composite (LMNO@LNO) possesses a more stable
and harmonious interface due to the higher bonding strength between
LiNbO3 and the transition phase. Therefore, LMNO@LNO demonstrates
the most outstanding rate capability and long-tern cycling stability
(decay rate of 0.041% per cycle during 1000 cycling at 5 C). This
work provides a new inspiration for the coating materials selection
and the interface stability research for the LMNO cathodes.
A La4NiLiO8-coated LiNi0.8Co0.1Mn0.1O2 cathode was synthesized by solid-phase sintering, with Ni ions from the host material involved in La4NiLiO8 formation. This strengthened the bonding between the coating and host cathode, and improved the cathode's structural stability.
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