Abnormal Excess Capacity of Conjugated Dicarboxylates in Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are considered to be key energy storage systems needed to secure reliable, sustainable, and clean energy sources. Redox-active organic compounds have been proposed as interesting candidates for electrode materials for the next-generation LIBs because of their flexible molecular design, recyclability, and low production cost. Despite wide interest, a molecular-level understanding of the electrochemical lithiations/delithiations of those materials remains rudimentary. We synthesized a set of π-conjugated dicarboxylates and discovered unprecedented excess capacities for inverse-Wurster-type nonfused aromatic compounds (dilithium terephthalate and dilithium thiophene-2,5-dicarboxylate). Molecular structural investigations based on solid-state CP/MAS (13)C NMR combined with the stable isotope labeling method and ex situ X-ray diffraction were carried out to elucid…