Surface reconstruction via rapid solution quenching to enhance structural stability of lithium-rich layered cathodes

Lithium-rich layered oxides (LLOs) are prospective materials for future-generation cathodes attributable to their high specific capacity. However, significant surface instability, particularly under high-voltage operating conditions, leads to substantial voltage decay and dramatic capacity degradation during long-term cycling, severely limiting their widespread application. In this study, we developed a universal brine quenching strategy to construct a stabilized composite surface structure for LLOs. This structure comprises an inner surface layer with a Y-doped layered structure and an outermost layer featuring a disordered rock-salt structure. Doping in the layered structure strengthens the Y-O bonds, raises the energy barrier for oxygen evolution, and significantly increases the stability of the lattice oxygen. Additionally, the disordered rock-salt surface structure reduces oxygen release during the charge and discharge cycles. Consequently, this well-designed surface structure significantly boosts the structural stability of the LLO surface, suppresses structural degradation during long-term cycling, and facilitates Li+ diffusion kinetics. The improved redox activity, combined with superior structural stability, contributes to an outstanding electrochemical performance. For instance, the Y-quenched Li1.2Mn0.54Ni0.13Co0.13O2 cathode exhibited an improved discharge capacity of 283 mAh g−1 at 0.1 C and 223 mAh g−1 at 1 C, along with remarkable cyclic stability retaining 91.2% of its capacity after 300 cycles at 1 C, and a reduced voltage decay of 1.18 mV cycle−1 (compared to 1.53 mV cycle−1 for pristine LLO). This research provides valuable insights into the design and synthesis of high-energy-density LLOs through a simple and cost-effective strategy.