High-Performance PB-KZnHCF Electrochromic Devices Enabled by a Synergistic K+/Zn2+ Dual-Ion Electrolyte

A K⁺/Zn²⁺ dual-ion electrolyte is proposed to suppress dissolution and stabilize KZnHCF counter electrodes. • The electrolyte ensures high electrochemical activity for both the PB working electrode and the KZnHCF counter electrode. • The optimized PB-KZnHCF device achieves a large optical modulation, fast switching speed, and excellent cycling stability. KZnHCF (K 2 Zn 3 [Fe(CN) 6 ] 2 ), a typical Prussian blue analog (PBAs), exhibits high transparency regardless of the redox states, making it an ideal transparent counter electrode material for electrochromic devices. However, its cycling durability is seriously limited by stability issues deriving from material dissolution. In this work, we propose a K + /Zn 2+ dual-cation electrolyte to enhance the cycling durability of KZnHCF by changing the Zn 2+ dissolution equilibrium between the electrolyte and the electrode. This electrolyte formulation is also compatible with the Prussian Blue (PB) electrochromic electrodes, enabling excellent electrochromic performance. Based on these merits, a high-performance electrochromic device is constructed by pairing the PB working electrode with the KZnHCF counter electrode in the K + /Zn 2+ electrolyte. This device demonstrates a desirable optical modulation of 52.7% at 633 nm with a coloration and bleaching response time of 5 and 14 s, respectively. After 1000 cycles, 77.8% of the initial optical modulation retains, indicating a decent cycling stability. This work underscores the promise of electrolyte engineering in addressing stability challenges of electrodes, offering a viable pathway to improve the performance of Prussian blue (PB)-based electrochromic devices. Download: Download high-res image (107KB) Download: Download full-size image