Alloy/Perovskite Compounds Modified by Plasma Treatment and their Role in Enhancing the Capacitance of Sustainable Graphene Supercapacitors

Abstract Graphene electrodes were firstly printed on recycled single‐use‐packets. Later, the Ni 50 Mn 35 In 15 (NMI) alloy or Ca 2.9 Nd 0.1 Co 3.9 Cu 0.1 O 9 , (CNCCO) misfit perovskite was deposited on the graphene electrodes to enhance their capacitive performance. Next, flexible supercapacitors (SCs) were assembled by using such electrodes. The SCs made with NMI and CNCCO powders were named as GNMI‐SC, and GCNCCO‐SC, respectively. Those ones produced capacitances/energy‐densities of 761.8 F g −1 /152.6 Wh kg −1 and 207.7 F g −1 /41.6 Wh kg −1 , respectively. Subsequently, a mixture 1 : 1 of NMI and CNCCO powders was melted/coalesced at 1700 °C by using a plasma treatment in argon atmosphere and obtained in this way a NMI/CNCCO composite powder. The SC made with this last composite generated a capacitance/energy‐density of 1235.2 F g −1 /247.3 Wh kg −1 . Those last values are 62–500 % higher than these for the GNMI‐SC, and GCNCCO‐SC devices. Other benefits obtained after the introduction of the NMI/CNCCO powders into the SCs were: 1) the formation of additional Cu 2+ , Mn 4+ , Nd 2+ and In 3+ species, which enhanced the capacitance; 2) the capacitance retention was maintained above 93 % after 500 cycles of charge discharge; and 3) the lowest values of series and charge transfer resistances were obtained, which favored the ion diffusion/storage in the SC electrodes.