High-Performance Supercapacitors Using Hierarchical And Sulfur-Doped Trimetallic NiCo/NiMn Layered Double Hydroxides

Abstract

A supercapacitor features high power density and long cycling life. However, its energy density is low. To ensemble a supercapacitor with high power- and energy-densities, the applied capacitor electrodes play the key roles. Herein, a high-performance capacitive electrode is designed and grown on a flexible carbon cloth (CC) substrate via a hydrothermal reaction and a subsequent ion exchange sulfuration process. It has a 3D heterostructure, consisting of sulfur-doped NiMn-layered double hydroxide (LDH) nanosheets (NMLS) and sulfur-doped NiCo-LDH nanowires (NCLS). The electrode with sheet-shaped NMLS and wire-shaped NCLS on their top (NMLS@NCLS/CC) increases the available surface area, providing more pseudocapacitive sites. It exhibits a gravimetric capacity of 555.2 C g-1 at a current density of 1 A g-1, the retention rate of 75.1% when the current density reaches up to 20 A g-1, as well as superior cyclic stability. The assembled asymmetric supercapacitor that is composed of a NMLS@NCLS/CC positive electrode and a sulfurized activated carbon negative electrode presents a maximum energy density of 24.2 Wh kg-1 and a maximum power density of 16000 W kg-1. In this study, a facile strategy for designing hierarchical LDH materials is demonstrated as well as their applications in advanced energy storage systems. On a flexible carbon cloth, sulfur-doped NiMn-layered double hydroxides (LDH) nanosheets (NMLS) and sulfur-doped NiCo-LDH nanosheets (NCLS) are emerged into a 3D heterostructure. Using this NMLS@NCLS/CC positive electrode and a sulfurized activated carbon negative electrode, an ensembled asymmetric supercapacitor features high-performance, including high-power- and energy-densities as well as long-term stability.image