Achieving High‐Voltage Stability in Li‐Rich Ni‐Rich Oxides with Local W/Ni(Li) Superstructure

Abstract

AbstractCreating high‐energy‐density cathodes is crucial for building next‐generation lithium‐ion batteries. However, materials exploration along two main directions, namely Li‐rich or Ni‐rich oxides, has encountered bottlenecks. To get rid of the impasse, here a “Li‐rich Ni‐rich” route is consolidated by designing a new family of Li1+yNi(3‐5y)/3W2y/3O2 oxides with high‐voltage cycling stability up to 4.5 V and high capacities over 230 mAh g−1. It is discovered that W6+ is largely incorporated into the LiNiO2 lattice, forming W/Ni(Li) inverse honeycomb‐ordered nano‐domains. These Li‐rich domains enable reversible anionic redox, clearly demonstrated by X‐ray absorption spectroscopy, resonant inelastic X‐ray scattering, transmission electron microscopy, and nuclear magnetic resonance, which is linked to improved electrochemical performance. Furthermore, the incorporation of W6+ into the lattice proves to be the key to generating electrochemically active Li‐rich domains irrespective of Li stoichiometry given that a similar local structure is found in W‐substituted non‐Li‐rich oxides. This therefore implies the underestimated role of high‐valence cations in tuning the structure and electrochemistry of Ni‐rich oxides. These results underline the necessity of a Li‐rich composition in the request for reversible high capacity, reinforcing the promise of a “Li‐rich Ni‐rich” avenue for developing advanced cathodes.