A Combined Insertion-Conversion Process in Graphite: CuO Composite Enhances the Energy of Lithium-Ion Capacitors with Wide Operational Temperatures

Lithium-ion capacitors (LICs) are prime energy storage devices that meet the limitations of Lithium-ion batteries (LIBs) and Electrical double-layer capacitors, bringing energy and power simultaneously in a single device. Our LIC comprises a combined insertion-conversion mechanism in the battery-type electrode, and the cathode is the commercially available activated carbon. The conversion-type CuO and intercalation-type graphite were mixed uniformly via a mechanical planetary miller and used directly as the anode material. It is noteworthy to mention that the CuO and graphite were regenerated/recovered from the spent LIBs. The copper foil current collector of spent LIB was regenerated as the CuO using simple steps, and the graphite was recycled directly. Five different composites were prepared, and an electrochemical comparative study was performed among these composites. In addition, the performances were compared between two different binders: Polyvinylidene fluoride (PVdF) and Carboxymethylcellulose (CMC), in which the dominance of CMC was significantly observed. The Li-ion storage properties were investigated by pairing the composites with the Li-metal. All the composites exhibited better electrochemical performance in half-cell assembly. The interfacial properties, such as Solid Electrolyte Interface formation/depletion, were studied from the in-situ -impedance. The LIC fabricated, with prior pre-lithiation, exhibited an enhanced energy density of 175 Wh kg –1 with excellent cyclic stability for more than 10,000 cycles. The LIC was also adaptable to different climatic conditions as it was analysed by testing the electrochemical performance at various temperature conditions.