Enhanced long-term cyclability in Li-Rich layered oxides by electrochemically constructing a LixTM3-xO4-type spinel shell

The poor long-term cycling stability, including the fast capacity fade and the severe voltage decay, has become the main concern hindering the practical application of Li-rich layered oxides, a promising cathode for high-energy-density Li-ion battery. Herein, we design and electrochemically construct a ~10 nm-thick LixTM3-xO4-type (TM = Ni, Co, Mn, 0 < x < 1) spinel shell at the particle surface, which possesses both the good structural stability of TM3O4-type spinel phase and the good Li+ conductivity of LiMn2O4-type spinel phase. Systemic structural and electrochemical analysis demonstrate that, it slows down the activation rate of Li2MnO3 component and efficiently alleviates the lattice O loss at high voltage (>4.5 V) and Mn dissolution, thereby suppressing the structural degradation from the layered phase to the spinel phase in the bulk, eventually significantly enhancing the long-term cycling stability. This study adds richness into the Mn-based spinel phase system and provides a new heterostructure design strategy to improve the electrochemical performance of Li-rich layered cathodes and beyond.