Thermodynamics-directed bulk/grain-boundary engineering for superior electrochemical durability of Ni-rich cathode

Introducing high-valence Ta element is an essential strategy for addressing the structural deterioration of the Ni-rich LiNi1−x−yCoxMnyO2 (NCM) cathode, but the enlarged Li/Ni cation mixing leads to the inferior rate capability originating from the hindered Li+ migration. Note that the non-magnetic Ti4+ ion can suppress Li/Ni disorder by removing the magnetic frustration in the transition metal layer. However, it is still challenging to directionally design expected Ta/Ti dual-modification, resulting from the complexity of the elemental distribution and the uncertainty of in-situ formed coating compounds by introducing foreign elements. Herein, a LiTaO3 grain boundary (GB) coating and bulk Ti-doping have been successfully achieved in LiNi0.834Co0.11Mn0.056O2 cathode by thermodynamic guidance, in which the structural formation energy and interfacial binding energy are employed to predict the elemental diffusion discrepancy and thermodynamically stable coating compounds. Thanks to the coupling effect of strengthened structural/interfacial stability and improved Li+ diffusion kinetics by simultaneous bulk/GB engineering, the Ta/Ti-NCM cathode exhibits outstanding capacity retention, reaching 91.1% after 400 cycles at 1 C. This elaborate work contributes valuable insights into rational dual-modification engineering from a thermodynamic perspective for maximizing the electrochemical performances of NCM cathodes.