A new sodium iron phosphate as a stable high-rate cathode material for sodium ion batteries

摘要

Low-cost room-temperature sodium-ion batteries (SIBs) are expected to promote the development of stationary energy storage applications.However,due to the large size of Na+,most Na+ host structures resembling their Li+ counterparts show sluggish ion mobility and destructive volume changes during Na ion (de)intercalation,resulting in unsatisfactory rate and cycling performances.Herein,we report a new type of sodium iron phosphate (Na0.71Fe1.07PO4),which exhibits an extremely small volume change (~ 1%) during desodiation.When applied as a cathode material for SIBs,this new phosphate delivers a capacity of 78 mA·h·g-1 even at a high rate of 50 C and maintains its capacity over 5,000 cycles at 20 C.In situ synchrotron characterization disclosed a highly reversible solid-solution mechanism during charging/discharging.The findings are believed to contribute to the development of high-performance batteries based on Earth-abundant elements.