High Capacity and Energy Density Organic Lithium‐Ion Battery Based on Buckypaper with Stable π‐Radical

Abstract

Owing to an increasing demand on high performance and rare‐metal free energy storage systems, organic rechargeable battery has attracted much attention. To increase the capacity of the whole battery, we have fabricated coin‐type buckypaper cells composed of a trioxotriangulene neutral radical derivative (H3TOT) and single‐walled carbon nanotubes as a cathode and lithium metal plate as an anode without current collector. The cells exhibited a stable charge‐discharge behavior even at a 90 wt % H3TOT content with a high‐rate performance of 10 C originating from high electrical conductivity of H3TOT. Furthermore, based on the four‐stage redox ability of H3TOT, the H3TOT 90 wt % cathode showed a high capacity of approximately 260 mAh g−1 and a high energy density of 546 Wh g−1. In view of the simple fabrication of the cathode and excellent performance, TOT‐based buckypaper will open a new strategy for the flexible cells for next‐generation energy storages.

Rechargeable Batteries with 100% Cathode Active Materials─Conductive Vapor-Deposited Films of a Stable Organic Neutral Radical

“…In both cases, the capacity degradation was mainly caused by the dissolution and/or deformation of TOT microcrystals with the charge/discharge, since the separators of the cell after the battery test were stained with deep blue TOT anion salts (Figure g,h). Similar cycle degradation was also observed in high- TOT -content BP cathodes in our previous study . Although the cycle life is not high in comparison with those of other organic cathodes using polymer binders, the cycle life of the face-on TOT film cathode is surprisingly high considering that this cathode does not contain any polymer binders and carbon materials.…”

“…In the discharge curve, two sets of plateaus around 3.3–3.1 and 1.8–1.5 V were observed, and the capacity of the latter was larger than that of the former. These plateaus correspond to the redox between neutral radical to monoanion and monoanion to tetraanion species of TOT (Figure a) . The additional tailing capacity at the further lower voltage (1.5–1.0 V) may be derived from the capacity of the ITO/Al substrate.…”

“…Recently, we developed a new class of organic cathode active material showing a high charge storage capacity, 4,8,12-trioxotriangulene, a stable neutral radical even under air ( TOT , Figure a). − TOT exhibits a four-stage four-electron redox behavior from the neutral radical to radical tetraanion species (Figure a), and the pristine TOT possesses a quite high theoretical capacity of 334 mA h g –1 , assuming that four electrons are involved in the charge/discharge process. In the previous study, we reported a binder-free and metal current collector-free flexible BP cathode using TOT neutral radical as an active material . The TOT -based BP cathodes showed an efficient charge/discharge, and that with 90 wt % of TOT content showed a quite high capacity of 266 mA h g –1 , where the capacity was calculated based on the whole cathode.…”

Synthesis and Physical Properties of Trioxotriangulene Having Methoxy and Hydroxy Groups at α-Positions: Electronic and Steric Effects of Substituent Groups and Intramolecular Hydrogen Bonds

“…As previous research on our study on TOT , Bushby and co-workers synthesized the monoanion species of 1 and succeeded in the generation of its radical dianion and diradical trianion species, although the neutral radical 1 was not investigated . These redox features of TOT derivatives greatly contributed to the development of electronic functions such as a high-capacity organic rechargeable battery and an electrochemical catalyst for the oxygen reduction reaction . Furthermore, the TOT neutral radical also exhibits a strong self-assembling ability via “two-electron-multicenter bonding” based on the strong singly occupied MO (SOMO)–SOMO interaction to form a π-dimer or 1D π-stacking column, the latter of which causes the high electrical conductivity (Figure c). , We have designed and synthesized TOT derivatives having various substituent groups at the 2,6,10-positions (β-positions), and their electronic or steric effects highly affected on the electronic spin structure, redox properties and molecular packing controlling the physical properties, and functions of TOT derivatives …”

Electro-optical π-radicals: design advances, applications and future perspectives

“…These radicals are electrically conductive and This journal is © The Royal Society of Chemistry 2022 air-stable in the solid state, and even more so in their corresponding anionic forms (p-stacked crystals of 21 and TOT decompose at 195 and 4300 1C in air, respectively), making them very attractive for use as rechargeable energy storage materials in organic batteries. 170,171,178,179 TOT featured a strong NIR absorption band at 834 nm (ca. 2000 M À1 cm À1 at 300 K) in chloroform solution and the absorption was further enhanced on cooling (above 9000 M À1 cm À1 at 215 K) as a result of p-dimerization (Fig.…”