posted on 2022-07-13, 16:05authored byShin Gwon Lim, Mi-Sook Kwon, Taehun Kim, Hyeongi Kim, Suyeon Lee, Jungwoo Lim, Hanseul Kim, Kyu Tae Lee
Various Fe-based layered oxide materials have received
attention
as promising cathode materials for sodium ion batteries because of
their low cost and high specific capacity. Only a few P3-type Fe-based
oxide materials, however, have been examined as cathodes because the
synthesis of highly crystalline P3-type Fe-based oxides is not facile.
For this reason, the structural merits of the P3 structure are not
yet fully understood. Herein, highly crystalline P3-type Na0.67[Li0.1(Fe0.5Mn0.5)0.9]O2 heated at 900 °C is introduced to improve the
electrochemical performance of Fe-based layered oxides. The structures,
reaction mechanisms, and electrochemical performances of P3 Na0.67[Li0.1(Fe0.5Mn0.5)0.9]O2, P2 Na0.57[Li0.1(Fe0.5Mn0.5)0.9]O2, and P2 Na0.67[Fe0.5Mn0.5]O2 are compared
to demonstrate the roles of Li+ doping in the improved
electrochemical performance of P3 Na0.67[Li0.1(Fe0.5Mn0.5)0.9]O2, such
as stable capacity retention over 100 cycles. P3 Na0.67[Li0.1(Fe0.5Mn0.5)0.9]O2 significantly suppresses the migration of Fe3+ ions to tetrahedral sites in the Na layer during cycling because
the cation disorder of Li+ is more favorable than that
of Fe3+. As a result, P3 Na0.67[Li0.1(Fe0.5Mn0.5)0.9]O2 shows
better cycle performance than P2 Na0.67[Fe0.5Mn0.5]O2. P3 Na0.67[Li0.1(Fe0.5Mn0.5)0.9]O2 also
exhibits an improved rate performance compared to P2 Na0.67[Fe0.5Mn0.5]O2. This finding provides
fundamental insights to improve the electrochemical performance of
layered oxide cathode materials for sodium ion batteries.