Regulation of morphology and electronic configuration of NiCo2O4 by aluminum doping for high performance supercapacitors

Morphology engineering and element doping are two effective strategies to boost the capacitive performance of electroactive materials. The morphology control through doping process is conducive to simplifying the preparation process. Herein, an aluminum-doped (Al-doped) strategy was used to prepare Al-doped NiCo2O4 nanosheet-wire structure (Al-NiCo2O4 NSW) by hydrothermal method and subsequent calcination. The nanosheet-wire structure was composed of one-dimensional (1D) nanowires and two-dimensional (2D) ultrathin nanosheets. 1D nanowires can provide efficient pathways for the electrons/ions transport. 2D nanosheets can enlarge the specific surface area and expose more active sites. The Al doping can change the electronic structure of NiCo2O4 with enhanced electrical conductivity as revealed by density functional theory (DFT) calculations. Meanwhile, a strong adsorption capacity of OH- was obtained on Al-NiCo2O4 NSW for redox reactions. The Al-NiCo2O4 NSW electrode demonstrated a high specific capacity of 1441C g-1 (2446F g-1) at 1 A g-1 and excellent cycling stability (87.6% capacity retention at 10 A g-1 for 5000 charge-discharge cycles). The assembled asymmetric supercapacitor manifested a superior energy density of 46.2 Wh Kg-1 at a power density of 800 W kg-1.