Synergistic Bulk-Surface Modulation Stabilizing LiCoO₂ at 4.65 V via Zr-Pillaring and In Situ Lattice-Matching Engineering

Lithium cobalt oxide (LiCoO₂, LCO) is a critical cathode material for high-energy-density lithium-ion batteries, yet its application above 4.55 V (vs. Li/Li⁺) is severely limited by structural degradation via the O3→H1-3 phase transition, lattice oxygen loss, and cobalt dissolution. Here, we report a synergistic bulk-surface modification strategy combining Zr-pillaring (LZCO) with in situ LiCoPO₄ coating (LZCO@P) to stabilize LCO at 4.65 V. Zr-pillaring stabilizes the lattice and suppresses phase transition by expanding the O 2p-Co 3d band gap, as suggested by density functional theory (DFT), to mitigate oxygen redox activity. Lattice-matched interfacial engineering between LZCO and LiCoPO₄ coating results from interfacial P–O tetrahedral formation, which enhances mechanical adhesion and reduces oxygen surface reactivity of LZCO. Consequently, LZCO@P achieves 80.8% capacity retention after 1000 cycles at 1 C (3.5–4.65 V) and 91.2% after 1000 cycles at 3 C (3.5–4.65 V). A practical Li||LZCO@P pouch cell retains 92.3% capacity after 160 cycles at 1 C (3.0–4.6 V). The synergistic bulk-surface modification strategy contributes through different mechanisms and comprehensively improves the cycling stability of LZCO@P at 4.65 V.