A dispersed buffer phase enables mitigated stress toward stable 4.6 V Graphite||NCM811 batteries

Abstract

High-voltage Ni-rich cathodes, which show high energy density and large cost-effectiveness, hold great promise for power Li-ion batteries. However, the unstable cyclic structure rooted in stress restricts their practical applications. In this work, we propose a strategy using a dispersed Eu₂O₃ buffer phase to mitigate the high-voltage cyclic stress. The optimized Ni-rich cathode shows excellent high-voltage thermal stability and practical long-term cycling stability. For the constructed 4.6 V full cell, a superior capacity retention of 92 % after 200 cycles is observed. The enhanced cyclic properties are ascribed to the mitigated stress, as revealed by multi-characterizations such as in-situ X-ray diffractions and finite element simulation. As expected, the mitigated stress well stabilizes the oxygen lattice and preserves the particle structures. More importantly, the approach is confirmed to be versatile in other high-voltage cathodes. Also, other available elements including La and Dy for the construction of buffer phases are outlooked.