Lithiated Prussian blue analogues as positive electrode active materials for stable non-aqueous lithium-ion batteries

Prussian blue analogues (PBAs) are appealing active materials for post-lithium electrochemical energy storage. However, PBAs are not generally suitable for non-aqueous Li-ion storage due to their instability upon prolonged cycling. Herein, we assess the feasibility of PBAs with various lithium content for non-aqueous Li-ion storage. We determine the crystal structure of the lithiated PBAs via neutron powder diffraction measurements and investigate the influence of water on structural stability and Li-ion migration through operando X-ray diffraction measurements and bond valence simulations. Furthermore, we demonstrate that a positive electrode containing Li(2-x)FeFe(CN)(6)⋅nH(2)O (0 ≤ x ≤ 2) active material coupled with a Li metal electrode and a LiPF(6)-containing organic-based electrolyte in coin cell configuration delivers an initial discharge capacity of 142 mAh g(−1) at 19 mA g(−1) and a discharge capacity retention of 80.7% after 1000 cycles at 1.9 A g(−1). By replacing the lithium metal with a graphite-based negative electrode, we also report a coin cell capable of cycling for more than 370 cycles at 190 mA g(−1) with a stable discharge capacity of about 105 mAh g(−1) and a discharge capacity retention of 98% at 25 °C.