Calix[8]quinone: A new promising macrocyclic molecule as an efficient organic cathode in lithium ion batteries with a highly-concentrated electrolyte

Organic cathode materials have potential applications in rechargeable batteries due to their several advantages such as high specific capacity, flexible designability, plentiful raw materials, environmental friendliness, and renewability. However, their high solubility in organic electrolytes strongly impedes the further research progress. Thus, it is highly desirable to develop some new strategies to address this issue. Herein, we report one method to address this dissolution issue by increasing molecular weight without reducing theoretical capacity, where a novel Calix[8]quinone (C8Q) with 8 p-benzoquinone units connected by methylene groups was designed and prepared in a good yield (total: 23%). C8Q exhibits higher cycle stability (268 mAh g(-1)) in lithium-ion batteries (LIBs) compared to the same series of substances Calix[4]quinone (C4Q, 30 mAh g(-1)) and Calix[6]quinone (C6Q, 207 mAh g(-1)) after 100 cycles at 0.2 C. Moreover, C8Q shows better electrochemical performance in 4.2 M LiTFSI-AN highly-concentrated electrolyte with special aggregate structure configured with high-dissociation salt LiTFSI and low-viscosity solvent acetonitrile (AN), namely, C8Q possesses high capacity (340 mAh g(-1) after 100 cycles at 0.2 C), superior rate ability (440 mAh g(-1) at 0.1 C and 167 mAh g(-1) at 5 C), and ultra-long cycle life (220 mAh g(-1) after 1000 cycles at 0.5 C). This work could provide a promising strategy to address the dissolution issue of organic electrode materials in organic electrolyte.