Significant Role of Al in Ternary Layered Double Hydroxides for Enhancing Electrochemical Performance of Flexible Asymmetric Supercapacitor

Abstract

The Al effect on the electrochemical properties of layered double hydroxides (LDHs) is not properly probed, although it is demonstrated to notably promote the capacitive behavior of LDHs. Herein, ternary NiCo 2 Al x layered double hydroxides with varying levels of Al stoichiometry are purposely developed, grown directly on mechanically flexible and electrically conducting carbon cloth (CC@NiCo 2 Al x -LDH). Al plays a significant role in determining the structure, morphology, and electrochemical behavior of NiCo 2 Al x -LDHs. At an increasing level of Al in NiCo 2 Al x -LDHs, there is a steady evolution from 1D nanowire to 2D nanosheets. The CC@NiCo 2 Al-LDH at an appropriate level of Al and with the nanowire-nanosheet mixed morphology exhibits both significantly enhanced electrochemical performance and excellent structural stability, with about a 2.3-fold capacitance of NiCo 2 -OH. When applied as the anode in a flexible asymmetric supercapacitor (ASC), the CC@NiCo 2 Al-LDH gives rise to a remarkable energy density of 44 Wh kg −1 at the power density of 462 W kg −1 , together with remarkable cyclic stability with 91.2% capacitance retention over 15 000 charge-discharge cycles. The present study demonstrates a new pathway to significantly improve the electrochemical performance and stability of transition metal LDHs, which are otherwise unstable in structure and poorly performing in both rate and cycling capability.

Redox Tuning in Crystalline and Electronic Structure of Bimetal–Organic Frameworks Derived Cobalt/Nickel Boride/Sulfide for Boosted Faradaic Capacitance

“…The designed device can deliver an energy density of 45.0 Wh kg −1 at the power density of 857.7 W kg −1 . Even after the power density increased to 13.6 KW kg −1 , the device still demonstrates an energy density of 36.8 Wh kg −1 , outperforming most of the excellent energy storage devices (Figure e), such as nickel‐cobalt phosphate//AC, NiNTAS@Fe 2 O 3 //NiNTAS@MnO 2 , Ni 0.55 Co 0.45 C 2 O 4 //AC, Ni‐Co LDH@NF//NiCoO 2 @NF, CoNi‐MOF//AC, and CC@NiCo 2 Al‐LDH//CC@ZPC . Moreover, the asymmetric device shows excellent cycling stability with retention of 87.7% at a current density of 12 A g −1 after 5000 cycles (Figure f), suggesting the robust interconnected networks and reasonable strain accommodation of the hybrid electrode.…”

“…Extensive energy demands by portable electronics and electric vehicles have indorsed the rapid development of highly efficient energy storage technologies for human society . Electrochemical capacitors (ECs) have received significant attention as a strong candidate in virtue of high power density, fast charging rate, and long‐term cyclability . Since the performance metrics and energy storage mechanism of ECs depend on the electrode materials, extensive investigations have been performed to optimize the structure and electronic valence of inorganic materials to improve the energy density …”

Solid‐State Hybrid Supercapacitor Assembled from a Heterostructured Co−Ni Battery‐like Cathode and Supercapacitor‐Type Highly Disordered Carbon Nanosheets

“…The positions of cathodic and anodic peaks shifted to more negative and positive potential directions at higher scan rates, which can be ascribed to the electrode polarization effort . The kinetic features of the prepared sample during its operation were further analyzed by the CV measurements under different scan rates which are shown in Figure b and 2c.…”

“…The positions of cathodic and anodic peaks shifted to more negative and positive potential directions at higher scan rates, which can be ascribed to the electrode polarization effort. [18,21] The kinetic features of the prepared sample during its operation were further analyzed by the CV measurements under different scan rates which are shown in Figure 2b and 2c. The measured i is the sum of the slow diffusion controlled current (i diff ) and the surface capacitance dominated current (i cap ), which can be expressed by the power law in Equation (5) and Equation (6): [12,43,44]…”

Recent Advances of Two‐Dimensional Nanomaterials for Electrochemical Capacitors

“…c) Ragone plots of the ASC in comparison with some of those reported in the literature (for references referred to in the graph please see Ref. ). d) Cycling stability tested at 5 A g −1 .…”