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

Creating 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 Li_1+yNi_(3-5y)/3W_2y/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.