A multifunctional manipulation to stabilize oxygen redox and phase transition in 4.6 V high-voltage LiCoO₂ with sXAS and EPR studies

LiCoO₂, as a domain cathode material of Li-ion batteries, faces a great deal of challenges due to the limited cycling stability at high voltage (>4.35 V vs. Li/Li⁺). These issues are tentatively addressed here by a multifunctional self-stabilization modification strategy, involving trace Mg bulk doping, surface gradient Ti doping and BaTiO₃ dot coating in LiCoO₂. The multifunctional synergy is verified to overcome the detrimental irreversible phase transition and the growth of impedance of LiCoO₂ cycling at 4.6 V. By using soft X-ray absorption spectroscopy (sXAS) and electron paramagnetic resonance (EPR) techniques, we also elucidate that Ti surface gradient doping can reinforce the structure rigidity of the particles while significantly attenuates the irreversible oxygen redox at high voltage. All these strategies promote the prolonged cyclic performance of LiCoO₂ under 4.6 V high-voltage through different mechanism. This elaborate investigation provides an instructive contribution in the advancement of high-voltage LiCoO₂.