title: Enhanced Sodium Ion Storage Behavior of P2-Type Na(2/3)Fe(1/2)Mn(1/2)O2 Synthesized via a Chelating Agent Assisted Route.
abstract: On the basis of resource abundance and low cost, high capacity layered P2-type Na2/3Fe1/2Mn1/2O2 material is regarded as a potential cathode material for sodium-ion batteries but suffers from its unstable structure during cycling. In this work, P2-type Na2/3Fe1/2Mn1/2O2 layered materials were synthesized by a chelating agent assisted sol-gel method with NH3·H2O. With the addition of NH3·H2O and the control of the synthesis conditions, highly active material with a more stable structure and better electrochemical performance was obtained. Furthermore, the influences of structure changes during different voltage ranges (1.5-4.0 V and 1.5-4.3 V vs Na(+)/Na) on the Na(+) storage behaviors were also evaluated and compared. It is confirmed that, when being charged to 4.2 V, an OP4-type phase emerges, which can reduce the damage by the gilding of the MeO2 layers but leads to an unstable crystal structure. For long-term cycling, it is preferred to cut off at 4.0 V rather than at 4.3 V. For the optimized P2-type Na2/3Fe1/2Mn1/2O2 calcined at 900 °C, a discharge capacity of 92 mAh/g remains after 40 cycles in the voltage range of 1.5-4.0 V, and the Coulombic efficiency remains 100%.
authors.affiliation: Beijing Key Laboratory of Environmental Science and Engineering, School of Materials Science and Engineering, Beijing Institute of Technology , Beijing 100081, PR China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Bai
authors.affiliation: Beijing Key Laboratory of Environmental Science and Engineering, School of Materials Science and Engineering, Beijing Institute of Technology , Beijing 100081, PR China.
authors.forename: Lixiang
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Beijing Key Laboratory of Environmental Science and Engineering, School of Materials Science and Engineering, Beijing Institute of Technology , Beijing 100081, PR China.|Collaborative Innovation Center of Electric Vehicles in Beijing , Beijing 100081, PR China.
authors.forename: Chuan
authors.initials: C
authors.lastname: Wu
authors.affiliation: Beijing Key Laboratory of Environmental Science and Engineering, School of Materials Science and Engineering, Beijing Institute of Technology , Beijing 100081, PR China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: Beijing Key Laboratory of Environmental Science and Engineering, School of Materials Science and Engineering, Beijing Institute of Technology , Beijing 100081, PR China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Li
authors.affiliation: Beijing Key Laboratory of Environmental Science and Engineering, School of Materials Science and Engineering, Beijing Institute of Technology , Beijing 100081, PR China.|Collaborative Innovation Center of Electric Vehicles in Beijing , Beijing 100081, PR China.
authors.forename: Feng
authors.initials: F
authors.lastname: Wu
keywords: P2-type Na2/3Fe1/2Mn1/2O2; cathode; chelating agent; phase transition; sodium ion batteries; sodium ion diffusion