Improvement in Cycle Life of Organic Lithium-Ion Batteries by In-Cell Polymerization of Tetrathiafulvalene-Based Electrode Materials

Redox-active organic molecules are promising candidates for next-generation electrode materials. Nevertheless, finding low-molecular-weight organic materials with a long cycle life remains a crucial challenge. Herein, we demonstrate the application of tetrathiafulvalene and its vinyl analogue bearing triphenylamines as long-cycle-life electrodes for lithium-ion batteries (LIBs). These molecules were successfully synthesized using palladium-catalyzed C-H arylation. Electrochemical analysis revealed that a polymer formed on the electrode. LIBs comprising these molecules exhibited noteworthy charge-discharge properties with a long cycle life (the capacity after 100 cycles was greater than 90% of the discharge capacity in the third cycle) and a high utilization ratio (approximately 100%). "In-cell" polymerization during the first charge process is considered to contribute to the effect. This study indicates new avenues for the creation of organic materials for rechargeable batteries.

Periphery Modification of Tetrathiafulvalenes: Recent Development and Applications

Tetrathiafulvalene (TTF) and its analogs are fascinating molecules in materials science based on their excellent electron-donating abilities. This personal account describes recent advances in the synthesis of TTF analogs for functional materials via the palladium-catalyzed modification of peripheries of TTF analogs. We first consider three types of molecules: fluorophore-TTF hybrid molecules, multi-redox systems, and an organic ligand for metal-organic frameworks. These molecules were successfully synthesized via Stille coupling or palladium-catalyzed direct C-H arylation and their structural, electrochemical, and optical properties were clarified. Subsequently, phosphorus-substituted TTF analogs were successfully synthesized for future applications of redox-active phosphine ligands for metal catalysts. The development of these molecules can significantly affect the advancement of chemical science.

Synthesis and properties of tetrathiafulvalenes bearing 6-aryl-1,4-dithiafulvenes

Novel multistage redox tetrathiafulvalenes (TTFs) bearing 6-aryl-1,4-dithiafulvene moieties were synthesized by palladium-catalyzed direct C–H arylation. In the presence of a catalytic amount of Pd(OAc)₂, P(t-Bu₃)·HBF₄, and an excess of Cs₂CO₃, the C–H arylation of TTF with several aryl bromides bearing 1,3-dithiol-2-ylidenes took place efficiently to produce the corresponding π-conjugated molecules. We also succeeded in the estimation of the oxidation potentials and number of electrons involved in each oxidation step of the obtained compounds by digital simulations.

Fused Tetrathiafulvalene and Benzoquinone Triads: Organic Positive-Electrode Materials Based on a Dual Redox System

Fused donor-acceptor triads composed of two tetrathiafulvalenes (TTFs) and benzoquinone (BQ; 1) or naphthoquinone (NQ; 2) were successfully synthesized. X-ray structure analysis of the bis(n-butylthio) derivative revealed that the molecules are stacked in a head-to-tail manner. The bis(n-hexylthio)-1 exhibited six-pairs of one-electron transfer waves in the cyclic voltammogram, corresponding to the formation of both reduction and oxidation states from -2 to +4. The unsubstituted and bis(methylthio) derivatives of 1 and 2 were active materials in positive electrodes for rechargeable batteries, several of which displayed energy densities exceeding 800 mWh g^-1 . The bis(methylthio)-2 also functions as a positive electrode material for a rechargeable sodium-ion battery.