Probing the Nature of Li+/Ni2+ Disorder on the Structure and Electrochemical Performance in Ni-Based Layered Oxide Cathodes

Li+/Ni2+ disorder as an intrinsic structure defect in Ni-based layered oxides cathodes for lithium-ion batteries plays a crucial role on the overall electrochemical performances. However, the nature of Li+/Ni2+ disorder on the structure and property is still poorly understood. Herein, we design and synthesize layered LiNi1/3Co1/3Mn1/3O2 cathode materials with a different Li+/Ni2+ mixing degree, and focus on unveiling the influence mechanism of Li+/Ni2+ disorder on the surface/bulk structural evolution and the charge compensation mechanism by neutron, synchrotron radiation and electrochemical impedance techniques. High Li+/Ni2+ disorder increases the side reactions between electrolyte and electrode surface and aggravates the variation of local environment of Mn cations with (de)lithiating, which is largely responsible for the degradation of the initial capacity, rate capability and cycling performance. Interestingly, Li+/Ni2+ disorder can also relieve the electrostatic interaction between the cationic and anionic ions by enlarging the LiO6 octahedron and TMO6 octahedron, and locks the surrounding oxygen slabs by forming strong covalent bonds between antisite Ni and coordinated O ions, which alleviates the variations of the lattice parameters during charging/discharging. This study presents some new insights into designing high performance layered oxide cathodes through regulating Li+/Ni2+ disorder.