Understanding rhombohedral iron hexacyanoferrate with three different sodium positions for high power and long stability sodium-ion battery
RIS ID
143254
Abstract
© 2020 Elsevier B.V. Sodium iron hexacyanoferrate (NaFeHCF) has been considered as a potential cathode for sodium-ion batteries owing to its low-cost and easily prepared procedure. However, it is still challenging to achieve long cyclic stability and superior rate capability, and the sodium storage mechanism of sodium-rich NaFeHCF is still elusive. Herein, a sodium-rich NaFeHCF with rhombohedral structure is presented with excellent electrochemical performances within 2.0–4.2 V. The specific capacity of ~115 mA h g−1 is obtained by utilizing two plateaus around 2.9 and 4.06 V, respectively. Remarkable rate performance from 10 to 4000 mA g−1 and 1000 cycles with high capacity retention is achieved as well. Synchrotron powder X-ray diffraction (PXRD) and structural refinement reveals that sodium-ions occupy three different sites (interstitial, face and edge) in rhombohedral unit cell, which contribute different capacities on different plateaus during Na+ extractions. Moreover, the rhombohedral structure is well-maintained after long-term Na+ extractions/insertions and reversible phase transitions with small volume variation are observed through in-situ synchrotron PXRD. The kinetic properties of Na+ in rhombohedral unit cell are identified by ab-initio molecular dynamics method and density functional theory calculations, which indicate that Na+ transport on three-dimensional diffusion paths, thus enabling the outstanding rate performance of NaFeHCF.
Publication Details
Wang, W., Hu, Z., Yan, Z., Peng, J., Chen, M., Lai, W., Gu, Q., Chou, S., Liu, H. & Dou, S. (2020). Understanding rhombohedral iron hexacyanoferrate with three different sodium positions for high power and long stability sodium-ion battery. Energy Storage Materials, 30 42-51.