Fe-Based Coordination Polymers as Battery-Type Electrodes in Semi-Solid-State Battery–Supercapacitor Hybrid Devices

One two-dimensional Fe-based metal-organic framework (FeSC1) and one one-dimensional coordination polymer (FeSC2) have been solvothermally prepared through the reaction among FeSO₄·7H₂O, the tripodal ligand 4,4',4″-s-triazine-2,4,6-triyl-tribenzoate (H₃TATB), and flexible secondary building blocks p/m-bis((1H-imidazole-1-yl)methyl)benzene (bib). Given that their abundant interlayer spaces and different coordination modes, two compounds have been employed as battery-type electrodes to understand how void space and different coordination modes affect their performances in three-electrode electrochemical systems. Both materials exhibit outstanding but different electrochemical performances (including distinct capacities and charge-transfer abilities) under three-electrode configurations, where the charge storage for each electrode material is mainly dominated by the diffusion-controlled section (i ∝ v^0.5) through power-law equations. Additionally, the partial phase transformations to more stable FeOOH are also detected in the long-term cycling loops. After coupling with the capacitive carbon-based electrode to assemble into the semi-solid-state battery-supercapacitor-hybrid (sss-BSH) devices, the sss-FeSC1//AC BSH device delivers excellent capacitance, superior energy and power density, and longstanding endurance as well as the potential practical property.