Enhancing stability and rate performance of Li₂DHBQ cathodes in lithium-ion batteries via FEC-derived cathode–electrolyte interphase

Organic cathode materials present a promising alternative for the inorganic counterparts in conventional lithium-ion batteries (LIBs) due to lower cost, reduced environmental impact, renewability, and enhanced energy density. However, their practical application is hindered by dissolution in electrolytes, structural degradation, and sluggish lithium-ion transport. In this study, we introduce fluoroethylene carbonate (FEC) as an electrolyte additive to engineer a protective cathode–electrolyte interphase (CEI) layer, effectively mitigating cathode pulverization and enhancing battery stability of the organic cathode material, dilithium salt of 2,5-dihydroxy-1,4-benzoquinone (Li₂DHBQ). Electrochemical, morphological, and compositional analyses, including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), confirm that an optimal 1% FEC concentration forms a uniform CEI layer, significantly improving structural integrity and reducing interfacial resistance. Consequently, the battery with 1% FEC retains 185 mAh·g⁻¹ after 200 cycles at 500 mA·g⁻¹, with a capacity decay rate of just 0.049% per cycle, compared to 81 mAh·g⁻¹ and 0.302% per cycle for the FEC-free battery. Additionally, the 1% FEC battery exhibits a capacitive charge storage contribution of up to 93.7%, resulting in excellent rate performance. These findings underscore the crucial role of CEI engineering in stabilizing organic cathodes, offering a practical approach to achieving high-rate and long-cycle LIBs.