Monday, 30 May 2022
West Ballroom B/C/D (Vancouver Convention Center)
Electroactive organic materials (EOMs) are now widely studied to develop safer and greener energy storage systems. EOMs are very interesting for Li (or Na) batteries due to their very low cost, great sustainability with bio-sourcing possibilities, and their very high theoretical capacity. However, these organic materials suffer from great capacity fading due to their high solubility into common organic liquid electrolytes. A well-known EOM for Li batteries is 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) due to its electron acceptor character, its ability to react with lithium at high potential (3V vs. Li+/Li) and its high specific capacity (262.6 mA.h/g), although it suffers from high solubility in classic liquid electrolytes. Moreover, TCNQ displays a very flat voltage plateau in liquid cells and the reduced phases of TCNQ are very easy to obtain by direct chemical synthesis (reduction with lithium iodide for example). To solve the solubility problem, we investigated the feasibility of an all-solid-state organic battery using a solid electrolyte in which the EOM is not soluble. An inorganic electrolyte, namely argyrodite Li6PS5Cl, and a solid organic one were studied. Using those two electrolytes, the electrochemical performances of different TCNQ-based EOMs were analyzed: TCNQ itself, LiTCNQ obtained by direct chemical synthesis, and finally a charge-transfer supramolecular assembly with tetrathiafulvalene (TTF-TCNQ), cycled vs. Li-In alloy. The EOM/electrolyte interfacial reactivity and side-reactions during cycling were investigated by X-ray photoelectron spectroscopy (XPS).