Plentiful abutting functional groups boosting sodium storage in a small molecule

Abstract

Organic electrode materials (OEMs), particularly small molecules, are promising for the next-generation batteries due to their advantages of mass production with potentially low cost, flexibility, high capacity, and facile molecular design. However, small molecules usually have high solubility in organic electrolytes, resulting in low actual capacity and poor cyclability. Herein, we demonstrated a strategy that abutting functional groups could boost the performance via several aspects by utilizing a small molecule (QAPs) as a proof-of-concept. The QAPs contains plentiful abutting functional groups. We found that the abundant abutting functional groups could on one hand guarantee the high specific capacity, and on the other hand effectively boost the sodium storage by forming chelation with sodium ions. Moreover, due to the strong chelation effect, the complete extraction of Na ions required high potential, which led to the always existence of ionic intermolecular interactions and hence insolubility and high cyclability. As a result, the QAPs electrodes involved a reversible five-electrons redox process, delivering a high capacity of 562 mAh g-1 at 100 mA g-1, rate capability and long-term cyclability. The presence of chelation effect was substantially verified by high resolution mass spectrometry, control experiments and theoretical calculations.