Co-free Ni-rich layered oxide LiNi_0.8Mn_0.2O₂ has garnered considerable attention due to its high energy density and low cost. However, under high-voltage operation, its practical application suffers from severe lattice oxygen release and irreversible H2 → H3 transition, resulting in structural degradation and rapid capacity fading. To address this inconvenience, this study proposes a Fe/Zr codoping strategy: the incorporated Fe modulates the local transition metal–oxygen electronic environment and stabilizes the local oxygen coordination environment via Fe–O interactions, while Zr⁴⁺ exerts a lattice-anchoring effect through strong Zr–O bonding, thereby suppressing oxygen loss and detrimental phase transitions upon deep delithiation. The codoped cathode material retains a well-defined layered structure and exhibits superior electrochemical performance; it delivers a high reversible capacity of 207.06 mAh g⁻¹ at 0.1 C, achieves capacity retention of 81.55% after 200 cycles at 1 C, and maintains a high rate capability of 141.76 mAh g⁻¹ at 5 C. This study provides an effective doping strategy for stabilizing lattice oxygen and modulating charge compensation in Co-free Ni-rich cathode materials.

Nickel-rich layered oxides (NRLOs) are regarded as ideal cathode materials for high-energy-density all-solid-state lithium-ion batteries (ASSLIBs). However, their practical application is hindered by structural instability and interfacial reactions with sulfide solid-state electrolytes, which lead to rapid performance degradation. To address these challenges, a synergistic stabilization strategy has been developed, simultaneously reinforcing the bulk lattice of NRLOs and suppressing surface side reactions. In this approach, high-valence W⁶⁺ ions were incorporated into the lattice of LiNi_0.94Co_0.05Mn_0.01O₂ to enhance bulk-phase stability (W-NCM94), while excess W⁶⁺ ions segregated on the NCM94 surface, forming a protective Li_xW_yO_z passivation layer that effectively inhibits interfacial reactions. ASSLIBs fabricated with W-NCM94 cathodes exhibit superior electrochemical performance, delivering an initial capacity of 145.7 mAh·g⁻¹ at 0.2 C with outstanding cycling stability (>80% capacity retention after 230 cycles). Notably, at an elevated cut-off voltage of 4.5 V, the cells achieve an impressive initial capacity of 167.6 mAh·g⁻¹. This innovative strategy combining bulk doping with surface segregation provides new insights for designing stable, high-performance NRLOs-based ASSLIBs, paving the way for their practical implementation in next-generation energy storage systems.

Li-rich Mn-based oxides (LRMOs) hold great promise as next-generation cathode materials for high-energy Li-ion batteries because of their low cost and high capacity. Nevertheless, the practical application of LRMOs is impeded by their low initial Coulombic efficiency and rapid voltage decay. Herein, a V-doped layered-spinel coherent layer is constructed on the surface of a Co-free LRMO through a simple treatment with NH₄VO₃. The layered-spinel coherent layer with 3D ion channels enhanced Li⁺ diffusion efficiency, mitigates surface–interface reactions and suppresses irreversible oxygen release. Notably, V-doping significantly reduces the Bader charge of oxygen atoms, thereby impeding excessive oxidation of oxygen ions and further enhancing the stability of O-redox. The modified LRMO exhibites a remarkable initial Coulombic efficiency of 91.6%, significantly surpassing that of the original LRMO (74.4%). Furthermore, the treated sample showes an impressive capacity retention rate of 91.9% after 200 cycles, accompanied by a voltage decay of merely 0.47 mV per cycle. The proposed treatment approach is straightforward and significantly improves the initial Coulombic efficiency, voltage stability, and capacity stability of LRMO cathode materials, thus holding considerable promise for the development of high-energy Li-ion batteries.