Prolong Cycle-Life by Interlayer Doping and Vacancy Coupling Engineering in Li-rich Oxide Cathodes.

Although Li-rich layered oxides (LLOs) are widely favored due to their high capacity derived from oxygen anionic redox, the rapid degradation of the initial lattice shortens their cycle-life. This is mainly attributed to internal strain and irreversible degradation of the oxygen redox environment, leading to layered structure damage, phase transformation and oxygen vacancies, which accumulate rapidly with cycling. Mechanism exploration and modification development targeting individual factors have established the principles and effectiveness of transition metal (TM) dopes in the Li layer and cation vacancies in the TM layer for inhibiting layered phase degradation and promoting anionic reversible reactions, thereby inspiring coupling defects engineering. Here, we show that more permanent cycle-life (85.77 % capacity retention and 0.38 mV/cycle voltage decay after 500 cycles at 1C, 1C = 250 mAh g-1) can be achieved by constructing interlayer TM-vacancy coupling defects. The simultaneously obtained strong interlayer TM-O-TM ribbon, TM doping and TM-O interaction collectively and effectively maintain the layered framework and occupancy sequence, providing a stable coordination environment for oxygen redox. This work demonstrates the feasibility of constructing interlayer TM-vacancy coupling defects to pursue Li-rich cathodes with both high energy density and long cycle-life.