Lim Shin Gwon, Kwon Mi-Sook, Kim Taehun, Kim Hyeongi, Lee Suyeon, Lim Jungwoo, Kim Hanseul, Lee Kyu Tae
School of Chemical and Biological Engineering, Institute of Chemical Processes, Institute of Engineering Research, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea.
ACS Appl Mater Interfaces. 2022 Jul 13. doi: 10.1021/acsami.2c05784.
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 Na[Li(FeMn)]O 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 Na[Li(FeMn)]O, P2 Na[Li(FeMn)]O, and P2 Na[FeMn]O are compared to demonstrate the roles of Li doping in the improved electrochemical performance of P3 Na[Li(FeMn)]O, such as stable capacity retention over 100 cycles. P3 Na[Li(FeMn)]O significantly suppresses the migration of Fe ions to tetrahedral sites in the Na layer during cycling because the cation disorder of Li is more favorable than that of Fe. As a result, P3 Na[Li(FeMn)]O shows better cycle performance than P2 Na[FeMn]O. P3 Na[Li(FeMn)]O also exhibits an improved rate performance compared to P2 Na[FeMn]O. This finding provides fundamental insights to improve the electrochemical performance of layered oxide cathode materials for sodium ion batteries.
由于成本低且比容量高，各种铁基层状氧化物材料作为钠离子电池有前景的阴极材料受到了关注。然而，只有少数P3型铁基氧化物材料被研究用作阴极，因为合成高度结晶的P3型铁基氧化物并不容易。因此，P3结构的结构优点尚未得到充分理解。在此，引入在900℃下加热的高度结晶的P3型Na[Li(FeMn)]O，以改善铁基层状氧化物的电化学性能。比较了P3 Na[Li(FeMn)]O、P2 Na[Li(FeMn)]O和P2 Na[FeMn]O的结构、反应机理和电化学性能，以证明锂掺杂在改善P3 Na[Li(FeMn)]O电化学性能中的作用，如在100次循环中保持稳定的容量。P3 Na[Li(FeMn)]O在循环过程中显著抑制了铁离子向钠层四面体位置的迁移，因为锂的阳离子无序比铁更有利。结果，P3 Na[Li(FeMn)]O表现出比P2 Na[FeMn]O更好的循环性能。与P2 Na[FeMn]O相比，P3 Na[Li(FeMn)]O还表现出改善的倍率性能。这一发现为改善钠离子电池层状氧化物阴极材料的电化学性能提供了基本见解。
