A comparison of the electrochemical performance between novel donut-like and rectangular-like supercapacitors made with La0.5Pr0.5Fe0.7Mn0.3O3 perovskite

Novel donut-like supercapacitors (SCs) were fabricated from recycled plastics. To enhance their electrochemical performance, La 0.5 Pr 0.5 Fe 0.7 Mn 0.3 O 3 (LAFE) redox powder was added on their electrodes. This powder had an orthorhombic structure and was formed by porous grains with sizes of 40–120 nm according to the microscopy and X-ray diffraction analyses. Donut-like SCs (contained acidic electrolyte) made with and without LAFE had capacitances of 182.8 and 334.7 F g −1 , respectively. Although the device made with LAFE had lower capacitance, it presented a battery component (prolonged discharge at a stable voltage of 1.2 V), which produced a high capacity of 1555 mAh g −1 . In contrast, the donut-like SC made without LAFE had a lower capacity of 260 mAh g −1 . Other donut-like SCs were made with an amber electrolyte derived from recycled lithium-ion battery (LIB) electrodes (collected from expired LIBs). Those devices had lower capacitances and energy-densities of 96–230 F g −1 and 36–42 Wh kg −1 , respectively. For comparison purposes, rectangular SCs were fabricated with and without LAFE redox powder and obtained capacitances/energy-densities of 970.8 F g −1 /194.2 Wh kg −1 and 562.5 F g −1 /112.5 Wh kg −1 , respectively. Thus, adding the LAFE powder to the rectangular SCs incremented their capacitance by ⁓73 %. Those rectangular devices were also immersed in water at room temperature or under cold water (5 °C); consequently, the capacitance decreased by 45–53 %. The analysis by Raman spectroscopy, optical-absorption, and XPS spectroscopy demonstrated the existence of Fe 3+ /Fe 2+ and Mn 4+ /Mn 3+ species as well as oxygen-vacancy defects on the SC electrodes made with LAFE. Those ones promoted the storage of charge by redox-reactions. Hence, the results of this work revealed that donut-like energy sources can be fabricated from recycled six-pack rings, which avoids the contamination of the environment by microplastics. We also demonstrated that electrolytes can be produced from recycled LIB electrodes and could be used to fabricate efficient SCs. Both, the novel electrolyte and donut-like devices pave the way for the design of low-cost energy sources that can be used in wearable electronics. • supercapacitors with donut-like shape were constructed using recycled plastics. • Adding La 0.5 Pr 0.5 Fe 0.7 Mn 0.3 O 3 redox powder to SCs enhanced their capacitance/voltage by 72–77 %. • SCs with rectangular shape had 68 % higher capacitance than these with donut-like shape. • SCs with rectangular- and donut-like shapes produced maximum capacitance of 970.8 and 334 F g −1 , respectively. • Electrolyte fabricated from battery expired electrodes permitted capacitances up to 229.9 F g −1 .