Sodium-rich prussian blue analogue coated by poly(3,4-ethylenedioxythiophene) polystyrene sulfonate as superior cathode for sodium-ion batteries

Sodium-ion batteries (SIBs) are a promising alternative to complement costly lithium-ion batteries for grid-scale stationary energy storage systems. However, finding a suitable cathode material has been a challenging process mainly due to the large radius of sodium-ion that hinders the process of intercalation. In our previous work, we have successfully synthesized Prussian blue analogue (PBA) via simple single iron source precipitation and low thermal method. However, it suffered poor electrical conductivity. In this work, the as-prepared PBA (high purity, low vacancy (similar to 2%), and high sodium-ion content) was then coated with various concentrations of conductive polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT-PSS) via simple stirring method to aid the electron route. The coated PBA (PB-P5) demonstrates two-fold enhanced conductivity of 2.04 x 10(-5) S cm(-1) at 30 degrees C and 1.18 x 10(-4) S cm(-1) at 100 degrees C. XRD peaks of coated PBAs show a slight shifting to higher diffraction angle, indicating the changes from rhombohedral-like to cubic structure. The battery capacity retention has also improved from 73.9% (PB-P0) to 82.87% (PB-P5), on account of having PEDOT-PSS to slow down the side reaction between cathode and electrolyte and eventually improve the cycling stability. Additionally, PB-P5 displays the lowest potential separation in cyclic voltammetry (CV) and small charge transfer resistance, R-ct value, in which indicating a better electron transfer and enhanced overall conductivity. (c) 2023 Elsevier Ltd. All rights reserved.