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

Abstract

Organic molecules have attracted much attention for lithium-ion batteries owing to their flexibility, tunable performance through molecular design, and low cost. However, their high solubility in electrolytes and low conductivity hinder their utilization in battery applications. In this work, four organic charge transfer cocrystals were synthesized using p-fluoranil (FA) as the acceptor molecule and pyrene, benz[a]anthracene (BAA), chrysene and perylene as donor molecules. The resulting cocrystals demonstrated superior specific capacity and cycling stability compared to their 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 high specific capacity and cycling stability were attributed to the one-dimensional columnar structure and low solubility in the electrolyte of the cocrystals. This study indicates that charge transfer can effectively improve the specific capacity and cycling stability of organic small molecule-based Li-ion batteries.