Ionic\nLiquid-Assisted Prussian Blue for Stable Sodium-Ion\nBattery Cathodes

Abstract

Sodium-ion\nbatteries (SIBs) are bright competitors for large-scale\nenergy storage owing to infinite global reserves and the low cost\nof sodium. Prussian blue (PB) and its analogues are up-and-coming\ncathodes for SIBs due to their environmental friendliness, open framework,\nand facile preparation process. However, PB synthesized through traditional\nmethods shows several vacancies and structural defects, which results\nin structure collapse and inferior cycling performance. In this work,\nan ionic liquid is introduced into the PB structure (denoted as IL-PB),\nwhich greatly reduces the nucleation rate. Thus, IL-PB delivers a\nhigh specific capacity of 134 mAh g^–1 at 50 mA g^–1 and stable cycling performance with a capacity retention\nof 77.3% at 100 mA g^–1 after 500 cycles. The good\nproperty originates from the fewer vacancies and coordinated water\nin IL-PB materials. The reversible transformation mechanism of the\nIL-PB materials was further revealed by in situ characterizations.\nThe introduction of ionic liquid provides an idea for the preparation\nof high-quality PB materials.