Anion vacancy regulated sodium/potassium intercalation in potassium Prussian blue analogue cathodes for hybrid sodium ion batteries

10 January 2023, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Fe-based potassium Prussian blue analogues (K-PBAs) are traditionally used as K-ion battery cathodes. Interestingly, K-PBAs are appealing cathodes for Na-ion batteries (NIBs), due to the increased cation intercalation voltage compared to Na-PBAs. In such a hybrid NIB cell, where Na+ is in the electrolyte and K+ is in the PBA cathode, cation intercalation and electrochemical performance of the cathode can be significantly affected by [Fe(CN)6]4- anion vacancy. This work studies the effect of [Fe(CN)6]4- anion vacancy in K-PBAs on regulating K+/Na+ intercalation mechanism in hybrid NIB cells, by comparing two K-PBA cathodes with different vacancy contents. Experimental and computational results demonstrate that introducing a level of anion vacancy can maximize the number of K+ intercalation sites and enhance K+ diffusion in the PBA framework. This facilitates K+ intercalation and suppresses Na+ intercalation, resulting in a K+-dominated and high-discharge-voltage ion storage process in the hybrid NIB cell. The K-PBA cathode with 20% anion vacancy delivers 127 mAh g-1 at 50 mA g-1 and 63 mAh g-1 at 500 mA g-1, as well as retains 87% and 77% capacity after 100 and 300 cycles, respectively. It completely outperforms the counterpart with 7% anion vacancy, which exhibits increased Na+ intercalation but overall deteriorated ion storage. Our results show the promise of hybrid battery systems and the crucial role of vacancy regulation in designing electrode materials for these systems.

Keywords

Prussian blue analogue
Vacancy
Intercalation
Hybrid ion batteries
Sustainable

Supplementary materials

Title
Description
Actions
Title
Supporting information
Description
Results of MP-AES, TGA, FTIR, XANES, and elemental analysis of the samples, structural data of the Rietveld refinements, XRD patterns of BG and PW, additional XRD, Raman, XANES and soft XAS results of electrodes at intermediate states, and structural models of supercells.
Actions

Comments

Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.