Non-topotactic Transformation Pathway in Electrochemical Li + /Na + Ion-Exchanged Na-Mn-Fe Phosphates for Sodium-ion Batteries

Abstract

Herein, olivine-LiMn0.6Fe0.4PO4 is converted to triphylite-NaMn0.6Fe0.4PO4 via electrochemical ion-exchange, exhibiting unexpected non-topotactic phase transformation behavior. This cathode material demonstrates an energy density exceeding 400 Wh kg -1 in sodium-ion batteries. This study provides new insights into ion exchange chemistry. Figure 4. Electrode reaction kinetics of the IE-NFMP. (a) In-situ EIS spectra of the IE-NFMP electrode, along with the corresponding (b) DRT curves and (c) 3D projection surfaces. (d) GITT curves and (e) corresponding DNa+ calculation results.