Elucidating Influence of Mg ‐ and Cu‐Doping on Electrochemical Properties of O3‐Nax[Fe,Mn]O2 for Na‐Ion Batteries

O3 ‐Na5/6Fe1/3Mn1/2Mg1/6O2 is newly synthesized which delivers a high capacity of 196 mAh g−1 and is applicable to hard carbon // O3 ‐Na5/6Fe1/3Mn1/2Mg1/6O2 Na ‐ion cell. In addition to Mn3+/4+ and Fe3+/4+ redox, oxide ions participate in solid ‐state redox. Furthermore, randomly stacked intergrowth phases based on the ideal OP2‐type phase reversibly appear during sodium insertion and extraction. AbstractAlthough O3 ‐NaFe1/2Mn1/2O2 delivers a large capacity of over 150 mAh g−1 in an aprotic Na cell, its moist ‐air stability and cycle stability are unsatisfactory for practical use. Slightly Na‐deficient O3‐Na5/6Fe1/2Mn1/2O2 (O3 ‐Na5/6FeMn) and O3 ‐Na5/6Fe1/3Mn1/2Me1/6O2 (Me = Mg or Cu, O3 ‐FeMnMe) are newly synthesized. The Cu and Mg doping provides higher moist‐air stability. O3‐Na5/6FeMn, O3 ‐FeMnCu, and O3‐FeMnMg deliver first discharge capacities of 193, 176, and 196 mAh g−1, respectively. Despite partial replacement of Fe with redox inactive Mg, oxide ions in O3 ‐FeMnMg participate in the redox reaction more apparently than O3‐Na5/6FeMn. X ‐ray diffraction studies unveil the formation of a P‐O intergrowth phase during charging up to>4.0  V.

Source: Small - November 23, 2020 Category: Nanotechnology Authors: Yusuke Yoda, Kei Kubota, Kazutoshi Kuroki, Shinya Suzuki, Keisuke Yamanaka, Toyonari Yaji, Shota Amagasa, Yasuhiro Yamada, Toshiaki Ohta, Shinichi Komaba Tags: Full Paper Source Type: research