Choice of Binder on Conversion Type CuO Nanoparticles toward Building High Energy Li‐Ion Capacitors: An Approach Beyond Intercalation

Abstract In this work, the assembly of lithium‐ion capacitor (LIC) is described by pairing conversion type CuO nanoparticles recovered from the Cu current collector of spent lithium‐ion batteries (r‐CuO) as battery type electrode and activated carbon (AC) as the capacitor type electrode. The Li‐storage property of r‐CuO is studied in the presence of two binders (polyvinylidene fluoride, PVDF and carboxymethylcellulose, CMC) and found the aptness of CMC in comparison with PVDF. Accordingly, the Li/r‐CuO half‐cells with CMC binder exhibits better electrochemical performance such that even after 150 charge–discharge cycles, the cells could retain a specific capacity of ≈680 mAh g⁻¹ at a current density of 0.2 A g⁻¹. The assembled LIC (AC/r‐Cu⁰+Li₂O) having electrochemically pre‐lithiated r‐CuO phase with balanced mass loading of AC can exhibit a maximum energy density of 65.6 Wh kg⁻¹ with excellent cyclic stability at 2 A g−¹ for 10,000 cycles with ≈80% capacity retention. It is worth mentioning that the thus fabricated LIC shows decent performance at high (50 °C) and low (−5 and 10 °C) temperature conditions.