High mass loading NiCoAl layered double hydroxides with interlayer spacing and interface regulation for high-capacity and long-life supercapacitors

Abstract

To obtain high energy density supercapacitors (SCs) to meet the larger demand for electric vehicles and portable electronic products, increasing the mass loading of electrode materials without sacrificing electron and ion conductivity is an ideal avenue. Herein, stable α-phase NiCoAl hydroxides with an expanded interlayer spacing and superior electronic conductivity are efficiently synthesized via the coprecipitation method. Furthermore, the interface is ingeniously regulated by adjusting the proper concentration of the electrolyte to modulate the charge storage form of the electrode to resolve the structure collapse and block ion penetration/diffusion. As expected, the obtained NiCoAl-10 supercapacitor electrode under an ultrahigh mass loading (20.24 mg cm−2) has an ultrahigh area-specific capacitance of 23.85 F cm−2 at 10 mA cm−2, an excellent rate capability of 19.27 F cm−2, even at 40 mA cm−2, and an outstanding long-term cycling stability (87.5% capacity retention after 10,000 cycles). Ultimately, an asymmetric supercapacitor (ASC) device of NiCoAl-10//active carbon (AC) also exhibits a high energy density of 3.29 mWh cm−2 at 18.00 mW cm−2 and remarkable capacity retention. This work further interprets the energy storage mechanism of NiCoAl hydroxides under high mass-loading, and opens a new avenue for meeting the commercial application of high energy density SCs.