Lithium-rich layer oxides are expected to be high-capacity cathodes for next-generation lithium-ion batteries, but their performance is hindered by irreversible anionic redox, leading to voltage decay, lag, and slow kinetics. In order to solve these problems, we regulate the Ni/Mn spin state in Li_1.2Mn_0.6Ni_0.2O₂ by Be doping, which generates the superexchange interaction and activates Ni-t_2g orbitals. The activation of Ni-t_2g orbitals triggers the reductive coupling mechanism between Ni/O, which improves the reversibility and kinetics of anionic redox. The strong π-type Ni-t_2g/O-2p interaction forms a stable Ni-(O–O) configuration, suppressing excessive anion oxidation. In this work, the Be modified cathodes have good cycle stability, 0.04 mAh/g and 0.5 mV decay per cycle over 400 cycles at 1 C (60 min, 250 mA g⁻¹), with a rate performance of 187 mAh/g at 10 C (6 min, 2500 mA g⁻¹), providing a strategy for stabilising oxygen redox chemistry and designing high performance lithium-rich cathodes.