Single-walled carbon nanotubes/Ni–Co–Mn layered double hydroxide nanohybrids as electrode materials for high-performance hybrid energy storage devices

Abstract

Nanohybrids which combine SWCNTs and Ni–Co–Mn layered double hydroxides are prepared by a facile hydrothermal process and investigated for the first time as electrode materials for hybrid energy storage devices. The nanohybrid made with a precursor weight ratio of SWCNTs and Ni–Co–Mn layered double hydroxide of 10:90 exhibits the highest capacity of 912 C g−1 at 1 A g−1, while the nanohybrid made with a precursor weight ratio of 30:70 shows the highest rate retention of 65% from 1 A g−1 (672 C g−1) to 50 A g−1 (435 C g−1) and the best capacity retention of 70% after 10000 cycles. Moreover, the charge transfer mechanism of the Ni–Co–Mn layered double hydroxides during charge/discharge is investigated through in-situ X-ray absorption near-edge spectra. To demonstrate practical hybrid energy storage applications, two nanohybrid//SWCNTs asymmetric energy storage devices are assembled and tested in pouch cell configuration. Their performances under folded condition are also evaluated, revealing great potential for flexible hybrid energy storage applications.