Azo‐Group‐Containing Organic Compounds as Electrode Materials in Full‐Cell Lithium‐Ion Batteries

Abstract Inorganic compounds, including graphite, transition metal oxides, and chalcogenides, are widely used as electrode materials in rechargeable lithium‐ion batteries (LIBs). However, environmentally friendly and cost‐effective alternatives are pursued by focusing on the molecular design of organic materials that could be potential electrode materials in next‐generation LIBs. Herein, we study the utilization of an organic compound, azobenzene 4,4‐dicarboxylate lithium (ADL), as a negative electrode in full‐cell LIBs. The full‐cell LIBs are assembled by using ADL as the negative electrode, LiCoO 2 (LCO/ADL) or LiFePO 4 (LFP/ADL) as the positive electrode, and 1 M LiPF 6 dissolved in ethylene carbonate/diethylene carbonate (EC : DEC=1 : 1 by volume) as the electrolyte. Then, ex situ X‐ray diffraction (XRD), ex situ X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were carried out to understand the charge storage mechanism and structural changes during the electrochemical reaction. From the charge/discharge measurements, LFP/ADL rendered a higher specific capacity retention (88.05 %) than LCO/ADL full‐cells (73.79 %) after 200 cycles at a current density of 100 mA g −1 . The XPS analysis revealed that the deposition of metallic Li on the ADL anode in LCO/ADL full‐cells led to rapid capacity decay and inferior cyclic performance, whereas Li‐free metal deposition had been observed on the ADL anode in LFP/ADL full cells, which explained the higher cyclic stability and capacity retention rate in LFP/ADL full‐cells. The present study provides useful insights into the development and practical utilization of organic electrodes in next‐generation Li‐ion battery technology.