title: Abnormal excess capacity of conjugated dicarboxylates in lithium-ion batteries.
abstract: 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 elucidate the origin of the excess reversible capacity. Interestingly, an open-chain-type dilithium muconate did not show an analogous behavior, signifying the key role played by the cyclic moiety in the electrochemical reaction.
authors.affiliation: School of Energy and Chemical Engineering, KIER-UNIST Advanced Center for Energy, Ulsan National Institute of Science and Technology (UNIST) , UNIST-gil 50, Ulsan 689-798, Republic of Korea.
authors.forename: Hyun Ho
authors.initials: HH
authors.lastname: Lee
authors.forename: Yuwon
authors.initials: Y
authors.lastname: Park
authors.forename: Kyoung-Hee
authors.initials: KH
authors.lastname: Shin
authors.forename: Kyu Tae
authors.initials: KT
authors.lastname: Lee
authors.forename: Sung You
authors.initials: SY
authors.lastname: Hong
keywords: anodes; excess capacity; lithium-ion batteries; organic electrode materials