Enhancing the Reversibility of Lattice Oxygen Redox Through Modulated Transition Metal–Oxygen Covalency for Layered Battery Electrodes

Abstract

Utilizing reversible lattice oxygen redox (OR) in battery electrodes is an essential strategy to overcome the capacity limitation set by conventional transition metal redox. However, lattice OR reactions are often accompanied with irreversible oxygen oxidation, leading to local structural transformations and voltage/capacity fading. Herein, it is proposed that the reversibility of lattice OR can be remarkably improved through modulating transition metal–oxygen covalency for layered electrode of Na‐ion batteries. By developing a novel layered P2‐Na0.6Mg0.15Mn0.7Cu0.15O2 electrode, it is demonstrated that the highly electronegative Cu dopants can improve the lattice OR reversibility to 95% compared to 73% for Cu‐free counterpart, as directly quantified through high‐efficiency mapping of resonant inelastic X‐ray scattering. Crucially, the large energetic overlap between Cu 3d and O 2p states dictates the rigidity of oxygen framework, which effectively mitigates the structural distortion of local oxygen environment upon (de)sodiation and leads to the enhanced lattice OR reversibility. The electrode also exhibits a completely solid‐solution reaction with an ultralow volume change of only 0.45% and a reversible metal migration upon cycling, which together ensure the improved electrochemical performance. These results emphasize the critical role of transition metal–oxygen covalency for enhancing the reversibility of lattice OR toward high‐capacity electrodes employing OR chemistry.

Suppressing the Dynamic Oxygen Evolution of Sodium Layered Cathodes through Synergistic Surface Dielectric Polarization and Bulk Site‐Selective Co‐Doping

“…[17b,30] This argument is further supported by the different evolutions of NiNi/Mn bond distances (2.850 Å for NNMO and 2.859 Å for CTO@NNMO at the fully charged state; 2.893 Å for NNMO and 2.918 Å for CTO@NNMO at fully discharged state) (Figure S21b, Supporting Information), considering the fact that the bond distance of TMTM is greatly influenced by that of TMO because of the edgeshared octahedral structure. [24,31] Note that similar MnO and MnTM bond distance evolution is also observed for NNMO and CTO@NNMO during cycling (Figure S21c,d, Supporting Information), implying the presence of irreversible Mn migration for NNMO as well.…”

Modulation of Local Charge Distribution Stabilized the Anionic Redox Process in Mn-Based P2-Type Layered Oxides

“…According to the corresponding lattice parameters, the cell volume is further calculated. The maximum volume change during the whole cycle is only 3.5%, which proves that the structural distortion and damage are minimal, contributing to a better cyclic stability. , …”

Prolonged lifespan of initial-anode-free lithium-metal battery by pre-lithiation in Li-rich Li2Ni0.5Mn1.5O4spinel cathode

“…A quantitative parameter, the Debye–Waller factor ( σ 2 ), was adopted to estimate the relative structural disorder between the adjacent atoms around the target atom ( i.e. , Mn and Ni), 48 as exhibited in Fig. 2f .…”