Napthalene diimide derivative based organic cocrystal frameworks as cathode electrodes for stable lithium batteries

Abstract

Two charge-transfer cocrystals using 1,4,5,8-naphthalenetetracarboxylic diimide derivatives (NDIs) as donor block and coronene as acceptor segment were synthesized through solution centrifugation and investigated as cathode electrodes in lithium-ion batteries (LIBs). These cocrystals showed 1 : 1 mixed stacking with columnar structure, good thermal stability, and narrow band gaps of 2.24 eV or 2.34 eV. Via alkyl terminal tuning, methyl-NDI based complex (CN-1) displayed lower binding ability than propyl substituted complex (CN-3) and could undergo a crystal transition into a new solvent-free phase with void-rich architecture. LIB based CN-1 cocrystal as cathode electrode showed a specific capacity of up to 230 mA h g⁻¹ with long cyclability over 600 cycles due to its unique void-rich columnar and deformable structure. The lithiation and delithiation sites on aromatic backbones were testified by experimental and calculated results. This study thus not only provides a novel kind of organic cathode material but also proves that donor–acceptor complexes are promising candidates for the development of high-performance cathodes for LIBs.