Accelerating lattice oxygen kinetics of layered oxide cathodes via active facet modulation and robust mechanochemical interface construction for high-energy-density sodium-ion batteries

Abstract

Triggering anionic redox reactions (ARRs) offers a powerful route to enhance the energy density of low-cost manganese-based layered oxides for rechargeable sodium-ion batteries (SIBs). However, the ARR process often results in irreversible lattice oxygen release, leading to significant structural distortions and rapid performance degradation. Herein, we propose a multifunctional tunnel interface engineering strategy that stabilizes P2-Na_0.75Li_0.25Mn_0.75O₂ (NLMO) by regulating active facets, suppressing lattice oxygen release, and enhancing air stability, thereby achieving desirable performance in terms of energy density and cycling stability. With protection of this tunnel layer, NLMO retains high anionic redox activity without irreversible oxygen release at high voltage, undergoing a simplified solid-solution reaction with minimal structural mechanical stress, which was confirmed by a series of advanced synchrotron radiation-based characterization methods as well as mechanical stress simulations. The tunnel-modified NLMO cathode delivers a high energy density of 649.6 Wh kg⁻¹ at 0.1 C within 1.5–4.4 V, and exhibits exceptional capacity retention (91.24%). Given the intrinsic advantages of the sophisticated tunnel interface and superior lattice matching, NLMO exhibits excellent Na⁺ diffusion kinetics and enhanced air stability, which further improves its practicality. The tunnel interface engineering in this work offers valuable insights into high-voltage cathodes for SIBs, emphasizing lattice oxygen stabilization and robust interfacial stability.