Unleashing the Kinetic Limitation of Co‐Free Li‐Rich Mn‐Based Cathodes via Ionic/Electronic Dual‐Regulation

Abstract

AbstractLi‐rich Mn‐based oxide (LRMO) are promising cathode candidates for next‐generation Li‐ion batteries with combined cost‐effectiveness and high specific capacity. Designing Co‐free LRMO can further leverage the low cost of this class of cathodes given the capacity can be maintained. However, implementing cobalt‐free LRMO cathode materials are hampered by their sluggish kinetics, resulting in low capacity and poor rate performance that underperform compared with their Co‐containing counterparts. Here, it is confirmed that the slow kinetics of Co‐free LRMO originates from the structural disorder caused by transition metals (TMs) migration at high voltages (above 4.5 V Vs. Li+/Li) and consequent irreversible oxygen redox process. Aware of this, Na+/F− is introduced in surficial lattice to alleviate these issues, ultimately achieving improved discharge voltage (≈0.2 V above 1 C, 1 C = 0.25 A g−1), exceptional cycle stability in pouch‐type cell (95.1% capacity retention in 1 C after 400 cycles at 25 °C, and 80.9% capacity retention after 300 cycles in 0.5 C at 45 °C) and excellent C‐rate performance (≈150 mA h g−1 at 5 C). The newly developed Na+/F− gradient design unleashes the surficial charge transfer kinetics limitation and greatly improves the lattice structure stability, consequently providing valuable guidelines for future high‐capacity LRMO cathode design.