Sb-Induced Coherent Twin-Phase Engineering for Structural Pinning and High-Voltage Stabilization of Ni-Rich Layered Cathodes

Abstract Ni-rich layered oxide cathodes received considerable research interest due to their high energy density, yet their cycling stability was severely limited by irreversible H2–H3 phase transition-induced lattice strain accumulation and lattice oxygen release, especially at high voltage. Here, we report a coherent twin-phase engineering strategy by doping trace antimony (Sb) to stabilize layered LiNi0.82Co0.12Mn0.06O2 (NCM) cathodes under deep delithiation. Aberration-corrected STEM reveals Sb-induced coherent twin phases that crystallographically connect layered and locally rocksalt-like domains while maintaining an intact layered oxygen framework. These coherent twin phases act as robust pinning interfaces that suppress irreversible H2–H3–induced c-axis contraction and mitigate anisotropic lattice stress during high-voltage cycling. Meanwhile, time-of-flight secondary ion mass spectrometry and theoretical calculations reveal that strengthened Sb–O bonding raises the oxygen-vacancy formation energy, stabilizing lattice oxygen and suppressing oxygen release, thereby preserving structural integrity and mitigating transition-metal dissolution. Benefiting from these synergistic stabilization effects, 0.75Sb-NCM exhibits a high discharge capacity of 209.61 mAh g–1 at 0.1 C and maintains 85.56% capacity retention after 200 cycles at 1 C within 2.8–4.5 V, significantly outperforming U-NCM (70.22%). This work highlights coherent twin phases as a robust structural pinning architecture for stabilizing Ni-rich layered cathodes at high states of charge.