Precise control on morphology of ultrafine LiMn2O4 nanorods as supercapacitor electrode via two-step hydrothermal method

TL;DR

This study develops a two-step hydrothermal synthesis method to produce ultrafine LiMn2O4 nanorods with high surface area, demonstrating superior supercapacitor performance with high capacitance and cycle stability in specific electrolytes.

Contribution

It introduces a novel two-step hydrothermal synthesis approach for precisely controlling LiMn2O4 nanorod morphology, enhancing supercapacitor electrode performance.

Findings

Achieved LiMn2O4 nanorods with diameters of 10-80 nm and high surface area.

Demonstrated high pseudo-capacitance of 653.5 F/g at 15 A/g.

Observed 93% capacity retention after 4000 cycles.

Abstract

We report three different synthesis routes while maintaining similar reaction conditions to choose an effective way to precisely control the growth of ultrafine one dimensional LiMn2O4 in the form of nanorods. We developed a novel method of mixing the precursors through hydrothermal, yielding low dimensional precursors for effective solid state reaction to synthesize the nanorods. However, to achieve these, highly uniform beta-MnO2 nanorods were initially grown as one of the main precursors. The uniformity observed in as grown beta-MnO2 nanorods using hydrothermal technique help to attract minute LiOH particles upon mixing over its highly confined nanoregime surface. This facilitated the solid state reaction between MnO2 and LiOH to develop one of the finest LiMn2O4 nanorods with diameters of 10 - 80 nm possessing high surface area of 88.294 m2/g. We find superior charge storage behaviour for these finely ordered 1D nanostructures as supercapacitor electrodes in KOH with K3Fe(CN)6 as electrolyte in contrast to Li2SO4. A high pseudo - capacitance of 653.5 F/g at 15 A/g is observed using galvanostatic discharge time with high retention capacity of 93% after 4000 cycles. The enhanced charge storage property may arise from the redox couple [Fe(CN)6]3n/[Fe(CN)6]4n and K+ ions of the electrolyte. To the best of our knowledge, we demonstrate for the first time the effectiveness of a two step hydrothermal method in tuning the supercapacitive behaviour of 1D LiMn2O4 in redox additive electrolyte.