Entropy-Engineered Fe-O-Ni Orbital Coupling Enables Durable Co-Free Ni-Rich Layered Cathodes.

Cobalt-free Ni-rich layered cathodes are promising for high-energy-density lithium-ion batteries, but their practical implementation is hindered by coupled Li/Ni cation disorder, lattice oxygen instability, and interfacial degradation originating from the unstable Ni-O electronic framework. Herein, we develop an entropy-engineered Co-free Ni-rich layered cathode, LiNi0.8Mn0.05Mg0.05Al0.05Fe0.05O2, in which multicomponent entropy engineering serves as a structural platform for targeted orbital-level regulation. Within the entropy-stabilized lattice, Mn, Mg, and Al contribute to lattice-strain accommodation and framework stabilization, while Fe serves as an important electronic-regulation component within the multicomponent framework. Strong Fe 3d-O 2p hybridization constructs Fe-O-Ni electronic coupling bridges and induces a σ-withdrawing effect, which lowers the Ni eg orbital energy by 0.92 eV and redistributes charge across the transition-metal-oxygen network. As a result, the regulated electronic structure is consistent with a reduced tendency for Li/Ni cation mixing. Meanwhile, the enhanced Fe-O covalency strengthens lattice oxygen binding and mitigates oxygen release during high-voltage delithiation. Benefiting from the synergistic effect of entropy-stabilized lattice engineering and Fe-associated orbital regulation, the designed LNMMAFO cathode delivers a reversible capacity of 204 mAh g-1 at 0.5 C and retains 88.3% capacity after 300 cycles, significantly outperforming the Fe-free counterpart. This work demonstrates that entropy engineering can provide an effective platform for constructing orbital-coupled electronic frameworks, offering a feasible strategy for durable Co-free high-Ni cathodes.