@article{Huang2026, 
author = {Rui Huang and Shaohua Luo and Qi Sun and Lixiong Qian and Shengxue Yan},
title = {Na-site K pillar and Na-O-Mg configuration regulate lattice oxygen freedom in Fe/Mn-based cathodes enabling reversible anionic redox chemistry},
year = {2026},
journal = {Nano Research},
keywords = {Na2/3Fe1/2Mn1/2O2, K/Mg-doping, P2/O3 phase, reversible anion redox chemistry, ultra-high capacity},
url = {https://www.sciopen.com/article/10.26599/NR.2026.94909220},
doi = {10.26599/NR.2026.94909220},
abstract = {The affordability of Fe/Mn-based cathodes renders them a highly competitive choice for sodium-ion batteries (SIBs). The path to commercialization for these cathodes is obstructed due to inherently slow kinetics and insufficient stability in ambient conditions. This work reports on the P2/O3-Na0.67K0.03Mn0.5Fe0.38Mg0.12O2 (NFM-KM2) cathode, where K/Mg co-doping confers outstanding sodium storage capacity and stability, with the mechanism elucidated in detail. A critical insight emerged from our analysis. Specifically, it regulated the lattice oxygen freedom to trigger and enhance the activity and reversibility of the anion redox reaction. In this way, K/Mg co-doping resolved the persistent challenge of harnessing anionic redox reaction (ARR): it demonstrated how modulating the oxygen’s local coordination and the lattice oxygen's degrees of freedom can effectively activate these reactions while ensuring their high-voltage reversibility. Leveraging this concept, NFM-KM2 integrated wonderful capacity (218.1 mAh g-1 at 0.1 C), stability (93.0%/85.9%, 100/200 cycles), rate capability (92.1%), and energy density (416.7 Wh kg-1). The study further deepened the understanding of structural evolution and charge compensation mechanisms. The findings elucidated how a specific local oxygen environment regulated lattice oxygen freedom to activate and sustain ARR, representing a paradigm shift in understanding inactive element doping and guiding innovative design of leverage reversible anionic redox chemistry in Fe/Mn-based systems.}
}