Crystalline-amorphous hybrid CoNi layered double hydroxides for high areal energy density supercapacitor.

Abstract

Crystalline-amorphous hybrid materials have garnered significant attention in the realm of energy storage, yet simultaneously regulating the morphological and electronic structure of crystalline-amorphous hybrid remains a challenge. Herein, crystalline-amorphous hybrid CoNi-layered double hydroxides (CA-CoNi-LDHs) were constructed by a facile chronoamperometry (i-t) electrochemical activation strategy, which allows for dual modulation of both structural transformations and electronic structure of CoNi-layered double hydroxides (CoNi-LDHs). Experimental results demonstrate that the construction of a crystalline-amorphous hybrid can effectively optimize both the morphological and electronic structure of CoNi-LDHs, expose abundant defects, and raise the concentration of active Ni²⁺ and Co³⁺ species, which are conducive to increasing the active sites for energy storage. The reduced adsorption energy for OH^-, the increased electron density near the Fermi energy level, coupled with the narrowed bandgap energy of CA-CoNi-LDHs are favorable for accelerating electron transfer and enhancing reaction kinetic. Consequently, the CA-CoNi-LDHs@CC electrode with high mass loading (18.8 mg cm^-2) delivers an impressive areal capacitance of 13,070 mF cm^-2 at 5 mA cm^-2, along with exceptional cycling stability. Moreover, the assembled asymmetric supercapacitor based on CA-CoNi-LDHs@CC possesses a high areal energy density of 0.71 mWh cm^-2 at a power density of 3.95 mW cm^-2. This work proves that construction of crystalline-amorphous hybrid materials is a viable strategy for achieving high energy density storage.