Rare Earth Ion-Doped -MnO₂Nanorods for an Asymmetric Supercapacitor

The limited electrical conductivity of manganese dioxide (MnO2) hinders its broad use as an electrode in all-solid-state supercapacitor devices (ASDs). To overcome this, trivalent gadolinium (Gd) and erbium (Er) ions are incorporated into MnO2, effectively addressing the issue. This involves synthesizing alpha-MnO2 nanorods infused with Gd and Er by using a modified chemical process. Through the creation of crystal defects, augmentation of electrical conductivity, and increased porosity, the electrochemical performance is significantly enhanced. Cyclic voltammetry and galvanostatic charge-discharge measurements within the range of -0.2 to +0.6 V unveil improved capacitance values of 798 and 647 F g(-1) at 1 A g(-1) current density for Gd- and Er-doped alpha-MnO2 respectively, maintaining 92.4% and 89.7% charge retention after 5000 cycles. Analysis reveals that both samples are primarily dominated by electric double-layer capacitance (EDLC). Furthermore, surface capacitance outweighs diffusion-controlled processes in the electrochemical storage mechanism. The Gd-doped alpha-MnO2 coated device depicts a peak energy density of 78.5 Wh kg(-1) at 106.01 W kg(-1) power density for 0.5 A g(-1) and maximum power density of 498.1 W kg(-1) at 9.13 Wh kg(-1) energy density for 3 A g(-1). Even a handcrafted 1 cm x 1 cm device achieves 2.252 V potential, effectively illuminating commercial LEDs.