Preparation of δ-MnO2 nanoplates for supercapacitors using ultrasonic-assisted liquid-phase co-precipitation technique

• A novel technique has been developed to prepare highly dispersed δ-MnO 2 nanoplates. • The δ-MnO 2 nanoplates has expanded interlayer spacing and a wide pore size distribution. • The δ-MnO 2 nanoplate-based symmetric supercapacitor has outstanding cyclic stability. Birnessite-type manganese dioxide (δ-MnO 2 ) electrode material for supercapacitors (SCs) encounters challenges associated with structural degradation and a reduction in capacitance, rendering the preparation of high-performance δ-MnO 2 via simple methods a significant challenge. In this study, a novel and facile ultrasonic-assisted liquid-phase co-precipitation technique has been developed to prepare highly dispersed δ-MnO 2 nanoplates with an expanded and disordered interlayer microstructure. The δ-MnO 2 nanoplates possess a suitable specific surface area and a wide pore diameter distribution. These structural features facilitate electrolyte ion transport and penetration, thereby enhancing the electrocapacitive properties of the electrode. When fabricated into symmetric SCs, the δ-MnO 2 nanoplate-based SCs exhibit excellent cyclic stability, retaining 106 % and 93 % of their initial capacitances after 10,000 cycles at 3 A g −1 in 2 M KOH and 2 M KOH + 0.1 M K 3 Fe(CN) 6 , respectively. This work presents a promising approach for preparation of electrode material with superior cyclic stability for SCs.