Co- and Ni-Based Electroactive Metal-Organic Frameworks for Stable Lithium Storage: Electrochemical and Charge-Storage Behavior in Response to Different Metal Centers

In this work, we successfully synthesized [Co(TTPA)3(TDC)2(H2O)]·4DMF·3H2O (1) and [Ni(TTPA)3(TDC)2(H2O)]·3DMF·H2O (2) by incorporating a redox-active tris[4-(1H-1,2,4-triazol-1-yl)phenyl]amine (TTPA) ligand and thiophene-2,5-dicarboxylate (TDC) as a second carboxylic linker. Redox behavior of 1 and 2 was elucidated by a solid-state electrochemical method. Solid-state in situ spectroelectrochemical experiments confirmed the formation of triphenylamine radical cations under anodic potential. There is a scarcity of the anode material investigated using an organic moiety from the triphenylamine core, so we decided to investigate its lithium-ion storage and its capacity. The half-cell lithium-ion battery (LIB) studies demonstrate that both 1 and 2 exhibited an efficient and reversible Li+ storage capability of 210 and 146 mA h g-1 at 0.5 A g-1 after 1000 cycles, respectively. Spectroscopic studies indicated that 1 and 2 remained stable despite more than 1000 cycles. Further systematic electrochemical and ex situ Fourier-transform infrared analyses depicted that the organic moiety plays an important role in the Li+ storage mechanism through a synergic contribution of a capacitive and diffusion-controlled process. Due to the different architecture of the structures 1 and 2, both demonstrated distinctive electrochemical and charge-storage behaviors.