Reversible high-voltage N-redox chemistry in metal-organic frameworks for high-rate anion-intercalation batteries

Because of the capacity limitation in traditional transition-metal oxide cathodes, the design of novel cathodes is vital for the performance enhancement in lithium-ion batteries. In this work, we propose a new anion-intercalation strategy for the design of metal-organic frameworks that can be used as high-voltage cathodes in lithium-ion batteries. A novel pcu-topology [Zn₄O₂(DAnT)₃(DMF)₄]·(DMF)₆ MOF is synthesized with enriched nitrogen active sites and porous cage structure. When applied as cathode with LiPF₆ based electrolyte, this MOF reaches the theoretical capacity of ∼60 mAh g^-1 at a current density of 100 mA g^-1 within high working voltage of 2.5-4.0 V versus Li/Li⁺. Even at a high current density of 1000 mA g^-1 (∼16C), half capacity can still be obtained. The reversible conversion of N/N⁺ and adsorption/desorption of PF₆^- were also examined by a series of ex situ characterizations including XPS, XRD, and FTIR, which clearly validates our strategy that permits good electrochemical performance at relatively high working potential.