Superexchange interaction regulates Ni/Mn spin states triggering Ni-t2g/O-2p reductive coupling enabling stable lithium-rich cathode

Abstract

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 Li1.2Mn0.6Ni0.2O2 by Be doping, which generates the superexchange interaction and activates Ni-t2g orbitals. The activation of Ni-t2g orbitals triggers the reductive coupling mechanism between Ni/O, which improves the reversibility and kinetics of anionic redox. The strong π-type Ni-t2g/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. Li-rich oxides face challenges such as voltage decay and slow kinetics due to irreversible anionic reaction. Here, authors activated the Ni-t2g orbitals through generating superexchange interactions via Be doping. By triggering the reduction coupling mechanism, the reversibility and kinetics of the anionic reaction are effectively improved.