Improved specific capacity and cycle stability of organic cocrystal lithium-ion batteries through charge transfer

Organic molecules have attracted much attention for lithium-ion batteries due to the flexibility, adjustable performance through molecular design, and low cost. However, the high solubility in electrolytes and low conductivity hindered their utilization in battery applications. In this work, four organic charge transfer cocrystals are synthesized by using p-fluoranil (FA) as the acceptor molecule and pyrene, benz[a]anthracene (BAA), chrysene and perylene as the donor molecules. The resulting cocrystals demonstrated superior specific capacity and cycling stability compared to its monomer counterparts. Specifically, the pyrene-FA cocrystal exhibited the highest reversible capacity of 206 mAh g-1 after 300 cycles at a current density of 0.1 A g-1, and maintained excellent cycling stability over 420 cycles. Even at a high current density of 1 A g-1, the pyrene-FA cocrystal displayed the highest reversible capacity of 250 mAh g-1 and remarkable cycling stability over 4500 cycles. The good high specific capacity and cycling stability attributed to the one-dimensional columnar structure and low solubility in the electrolyte of cocrystals. This study indicates that charge transfer can effectively improve the specific capacity and cycling stability of organic small molecules-based Li-ion battery.