Impact of Prussian Blue Particle Size Distribution on Electrochemical Performance of Gel Polymer Electrolyte-Based Na-Ion Cells

Lithium-ion batteries (LIBs) are one of the most advanced electrochemical energy storage technologies. However, the increasing demand for LIBs, coupled with problems related to availability and lack of manufacturing centers, has led to lithium market inflation. At this point, sodium-ion batteries (SIB) represent an economically and environmentally attractive alternative for LIBs. Prussian Blue cathodes (PB) have been extensively studied as cost-effective materials with volumetric variations that allow the accommodation of sodium ions in the structure. Herein, we present a quasi-solid Na-ion cell based on PB cathode and green gel polymer electrolyte (GPE). Nanometric and micrometric PB powders are synthesized and characterized using a wide variety of structural, compositional and electrochemical techniques. The effect of the PB particle size in combination with different electrolytes is investigated. Enhanced cell safety is obtained using a GPE prepared by following a novel green method that avoids using toxic organic solvents. All the tested cells report remarkable electrochemical performance, being the nanometric-PB/ GPE/ Na cell configuration the one with the highest specific capacity and almost no capacity loss after 100 cycles, outperforming analogous cells assembled with liquid electrolyte. This electrochemical stability is triggered by a robust electrode-electrolyte interphase.