Synergistic effect of Na enrichment and F modification on copper Prussian blue analogue nanoparticles for supercapacitors

Abstract

Prussian blue analogues (PBAs) are promising energy storage materials for supercapacitors. However, high defects and low activity are challenging for high-performance of PBAs. Herein, we propose a series of modified copper Prussian blue analogues (CFPs) with interface rearrangement followed by F modification and Na enrichment. The spectroscopic and electrochemical characteristics demonstrated the synergistic effect of F and Na, revealing the advantages of efficient electronic control and reaction sites synergism, which contributes to the high ion/electron transport and reversibility of CFPs. Benefitting from the reduced defects, optimized conductivity, and boosted electrochemically active surface and exposed active sites resulting from pre-stored Na and regulated F, the supercapacitor performance of CFP-3 has been improved, with a specific capacity of 182 F g⁻¹ at 1 A g⁻¹, and the rate capability is 82.4 % of the initial specific capacitance at 10 A g⁻¹, which is 4 times higher than that of unmodified CFP-0. Asymmetric CFP-3//CNT device achieves an energy density of 6.1 Wh kg⁻¹ at a power density of 1 kW kg⁻¹, and an energy density of 5.3 Wh kg⁻¹ at a power density of 7 kW kg⁻¹. After 10,000 cycles, the device still retains 82.4 %, showing good cyclic stability. This work proposes a new approach to improve the energy storage properties by rearranging the interfacial atomic and optimizing the electrochemically active sites, which provides a new guidance for designing high-performance supercapacitor materials.