Flexible metal–organic frameworks as superior cathodes for rechargeable sodium-ion batteries

Abstract

In response to the ever-increasing demand for grid-scale energy storage systems, sodium ion batteries (SIBs) working at ambient- or room-temperature are gaining much attention as promising alternatives because of the abundance and low cost of sodium resources. However, their adoption is significantly hampered by several issues, especially in terms of sluggish kinetics and capacity retention during cycling. Herein, flexible Prussian blue analogue FeFe(CN)₆/carbon cloth composites are synthesized using low temperature strategies and utilized as a potential host for sodium ion insertion. As a proof of concept, the composites demonstrate excellent electrochemical performance: a reversible specific capacity of 82 mA h g⁻¹ at 0.2C, good rate capability and long term cycling life with 81.2% capacity retention over 1000 cycles. Most significantly, this low-cost, scalable and low-temperature synthesis provides guidance for the design of other flexible materials that could have applications in wearable electronics, energy storage and conversion devices.