Prussian Blue Analogue Co3[Co(CN)6]2 Anode for Lithium-Ion Batteries: Operando Magnetometry Insights into Lithium Storage

Prussian blue analogues (PBAs) have attracted considerable attention as electrode materials due to their open framework structures and tunable compositions. In this study, a well-defined PBA material, Co3[Co(CN)6]2, was synthesized via a co-precipitation method and systematically evaluated as an anode for lithium-ion batteries. The material delivers a high reversible capacity of 537.4 mAh g−1 at a current density of 0.1 A g−1, and maintains 116.2 mAh g−1 even at 5 A g−1, demonstrating excellent rate performance and electrochemical stability. Remarkably, it retains 64.6 % of its initial capacity after 1000 cycles, highlighting its outstanding long-term cyclability. To gain insight into the lithium storage mechanism, operando magnetization measurement combined with ex situ X-ray photoelectron spectroscopy were employed, revealing the redox and spin-state transitions of cobalt ions during the electrochemical process. Furthermore, a full cell constructed with Co3[Co(CN)6]2 as the anode and LiFePO4 as the cathode exhibited stable electrochemical performance, confirming its potential for practical applications. This work not only introduces a promising PBA-based anode material, but also underscores the utility of operando magnetization measurement as a powerful tool for probing charge storage mechanisms.