<p>Lithium-rich manganese-based oxides (LMR) are highly attractive cathode materials for advanced lithium-ion batteries due to their exceptional specific capacity. However, their practical viability is often limited by structural degradation, voltage decay, and lattice oxygen loss, primarily associated with the activation of the Li₂MnO₃ phase. To overcome these challenges, we successfully synthesized iron-doped LMR cathode materials via a sol–gel method, utilizing Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ as a template. Structural characterizations revealed that Fe doping preserved the α-NaFeO₂ layered structure (R-3m) and monoclinic Li₂MnO₃ phase (C2/m), while Rietveld refinement indicated a beneficial expansion of the c-axis, promoting Li⁺ diffusion, and an increased proportion of the layered LiTMO₂ phase. Microscopic analysis showed that Fe doping led to smaller, more dispersed particles. Electrochemical evaluations confirmed that Fe-doped LMR exhibits significantly improved cycling stability and rate capability, maintaining a splendid specific capacity of 217.9 mAh g⁻¹ with 94.55% retention after 100 cycles at 0.1C, and notably reduced voltage decay. X-ray photoelectron spectroscopy (XPS) analysis elucidated that Fe doping elevates and stabilizes the Mn⁴⁺ content, alters internal charge distribution, and confirms the active participation of the Fe²⁺/Fe³⁺ redox couple. Crucially, the Fe-doped material demonstrated a profoundly lower oxygen vacancy concentration, signifying enhanced lattice stability and suppressed oxygen release during electrochemical cycling. These findings underscore Fe doping as an effective strategy for mitigating structural degradation and improving the electrochemical performance of lithium-rich cathode materials.</p>