Co-free Ni-rich layered oxide LiNi_0.8Mn_0.2O₂ has garnered considerable attention due to its high energy density and low cost. However, under high-voltage operation, its practical application suffers from severe lattice oxygen release and irreversible H2 → H3 transition, resulting in structural degradation and rapid capacity fading. To address this inconvenience, this study proposes a Fe/Zr codoping strategy: the incorporated Fe modulates the local transition metal–oxygen electronic environment and stabilizes the local oxygen coordination environment via Fe–O interactions, while Zr⁴⁺ exerts a lattice-anchoring effect through strong Zr–O bonding, thereby suppressing oxygen loss and detrimental phase transitions upon deep delithiation. The codoped cathode material retains a well-defined layered structure and exhibits superior electrochemical performance; it delivers a high reversible capacity of 207.06 mAh g⁻¹ at 0.1 C, achieves capacity retention of 81.55% after 200 cycles at 1 C, and maintains a high rate capability of 141.76 mAh g⁻¹ at 5 C. This study provides an effective doping strategy for stabilizing lattice oxygen and modulating charge compensation in Co-free Ni-rich cathode materials.