Li‐rich layered oxides (LLOs) can deliver almost double the capacity of conventional electrode materials such as LiCoO2 and LiMn2O4; however, voltage fade and capacity degradation are major obstacles to the practical implementation of LLOs in high‐energy lithium‐ion batteries. Herein, hexagonal La0.8Sr0.2MnO3−y (LSM) is used as a protective and phase‐compatible surface layer to stabilize the Li‐rich layered Li1.2Ni0.13Co0.13Mn0.54O2 (LM) cathode material. The LSM is MnOM bonded at the LSM/LM interface and functions by preventing the migration of metal ions in the LM associated with capacity degradation as well as enhancing the electrical transfer and ionic conductivity at the interface. The LSM‐coated LM delivers an enhanced reversible capacity of 202 mAh g−1 at 1 C (260 mA g−1) with excellent cycling stability and rate capability (94% capacity retention after 200 cycles and 144 mAh g−1 at 5 C). This work demonstrates that interfacial bonding between coating and bulk material is a successful strategy for the modification of LLO electrodes for the next‐generation of high‐energy Li‐ion batteries.

Li-rich layered oxides have attracted intense attention for lithium-ion batteries, as provide substantial capacity from transition metal cation redox simultaneous with reversible oxygen-anion redox. However, unregulated irreversible oxygen-anion redox leads to critical issues such as voltage fade and oxygen release. Here, we report a feasible NiFe2O4 (NFO) surface-coating strategy to turn the nonbonding coordination of surface oxygen into metal–oxygen decoordination. In particular, the surface simplex M–O (M = Ni, Co, Mn from MO6 octahedra) and N–O (N = Ni, Fe from NO6 octahedra) bonds are reconstructed in the form of M–O–N bonds. By applying both in operando and ex situ technologies, we found this heterostructural interface traps surface lattice oxygen, as well as restrains cation migration in Li-rich layered oxide during electrochemical cycling. Therefore, surface lattice oxygen behavior is significantly sustained. More interestingly, we directly observe the surface oxygen redox decouple with cation migration. In addition, the NFO-coating blocks HF produced from electrolyte decomposition, resulting in reducing the dissolution of Mn. With this strategy, higher cycle stability (91.8% at 1 C after 200 cycles) and higher rate capability (109.4 mA g–1 at 1 C) were achieved in this work, compared with pristine Li-rich layered oxide. Our work offers potential for designing electrode materials utilizing oxygen redox chemistry.

We use in operando Raman spectroscopy to investigate the structural evolution mechanism of transition metal cation and oxygen anion redox in Li-rich layered oxide cathodes. We directly capture the release of oxygen-driven electrolyte oxidation (especially the dimethyl carbonate component) at high-voltage operation (4.4 V).

Lithium−air batteries (LABs) are considered one of the most promising energy conversion systems for delivering large specific energy. However, practical applications still face major challenges, including poor rate capability, short cycle life, and low round‐trip efficiencies. Here, we report a novel strategy to improve the catalytic activity of MnO2 through the combination of 3D MnO2 and carbon nanotubes/carbon fiber paper (CNTs/CFP) with a binder‐free structure. Side reactions related to the binder are precluded in this design. The presence of CNTs not only promotes the formation of a 3D structure of the air electrode, but directs the uniform deposition of MnO2. When applied as a cathode in LABs, the as‐prepared MnO2/CNTs/CFP electrode achieves comparable specific capacity (with a discharge capacity of 8723.5 mAh g−1(CNTs+MnO2) at 100 mA g−1). The encouraging electrochemical performance is found to benefit from free‐standing nanoporous structures, which provide more active sites for enabling oxygen reduction. It is also attributed to the decreased side reactions.