Ferrocene-Based Mixed-Valence Metal–Organic Framework as an Efficient and Stable Cathode for Lithium-Ion-Based Dual-Ion Battery

Organic anion-hosting cathodes are remarkably attractive platform candidates for lithium-ion-based dual-ion batteries (LDIBs) due to their various advantages such as variety, designable, and adjustable. Here, a new organic anion-hosting mixed-valence metal–organic framework cathode (Co 2 II Co III (DFc) 2 (OH) 3 ·H 2 O, abbreviated as Co(DFc)x) is first employed in LDIBs. With the redox reactions happening in the couples of Fe 2+ /Fe 3+ and Co 2+ /Co 3+, PF 6 – anions can be incorporated into the cathode and reversibly released into the LiPF 6 -based electrolyte. Meanwhile, benefiting from its unique structure and insolubility, Co(DFc)x shows a high energy density of 632 Wh kg –1 (vs lithium anode), a high operating potential of 3.63 V (vs Li + /Li), a high reversible (discharge) capacity of 170 mAh g –1 at 50 mA g –1 (the third cycle), an excellent rate performance (up to 2000 mA g –1, 5 min for one cycle), and extraordinary cycling stability (an average capacity of 74.9 mAh g –1 for 8000 cycles at 2000 mA g –1 ).