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, Co 3 [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 Co 3 [Co(CN) 6 ] 2 as the anode and LiFePO 4 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. • Developed a straightforward co-precipitation route to synthesize Prussian blue analogue Co 3 [Co(CN) 6 ] 2 featuring a three-dimensional open-framework. • Demonstrated high reversible capacity and excellent rate capability across a broad range of current densities. • Exhibited robust long-term cycling stability with minimal capacity fade over extended cycles. • Leveraged operando magnetometry to elucidate cobalt redox and spin-state dynamics during lithium storage.