Rare Earth Ion-Doped α-MnO₂Nanorods for an Asymmetric Supercapacitor

Abstract

The limited electrical conductivity of manganese dioxide (MnO 2 ) 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 MnO 2 , effectively addressing the issue. This involves synthesizing α-MnO 2 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 α-MnO 2 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 α-MnO 2 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 × 1 cm device achieves 2.252 V potential, effectively illuminating commercial LEDs.