Pre-calcination time tuning: A Key to unlock high-performance Li-rich cathodes via biphase regulation

Lithium-rich manganese-based cathodes offer high capacity but suffer from voltage fade and capacity decay due to oxygen release and structural instability. While various modifications exist, achieving high-level mixing of the key C 2/ m and R -3 m phases remains challenging. This study presents a straightforward approach to control phase compatibility by tuning the pre-calcination time. We find that an 8-hour pre-calcination optimally enhances the mixing of the C 2/ m and R -3 m phases, minimizes grain size, and increases Mn 4+ and lattice oxygen content. This tailored microstructure suppresses side reactions and facilitates Li + diffusion. The resulting material delivers a high capacity of 254.3 mAh⋅g -1 at 0.1C and exceptional cycling stability with 98.1 % capacity retention after 250 cycles at 1C. This work highlights the critical role of pre-calcination in regulating phase structure and provides a practical route for developing high-performance lithium-rich cathodes.