Rare earth doped bimetal hydroxide/multi-walled carbon nanotubes as composite electrodes to achieve high-energy-density asymmetric supercapacitors

Abstract

A novel electrode material of Ni–Co bimetallic hydroxide composite multi-wall carbon nanotubes (La–NiCo LDH/MWCNTs/NF) doped with rare earth elements was prepared on nickel foam (NF) by a one-step hydrothermal method and doped with different concentrations of La3+ ions. The introduction of La3+ ions can increase the layer spacing of LDH materials. The acidification of MWCNTs on the surface of NF can also enhance the collection effect of NF. The synergistic effect of MWCNTs and La3+ ions further improves the specific capacitance of the material. At the current density of 1 A g−1, the maximum specific capacitance of the sample with 5 % La3+ ion concentration reaches 4396.0 F g−1, and the capacitance retention is 70.31 % after 3000 cycles of a single electrode. When assembled into a device, the device obtains a high energy density of 77.86 Wh kg−1 at a power density of 800.0 W kg−1. After assembling into an asymmetric supercapacitor, it has undergone 8000 cycles of performance testing, and the capacitance ratio is only reduced by 4.9 %. It shows good electrochemical cycle performance. This work provides a new way to study the doping of rare earth elements for supercapacitor materials.