Flexible and Mechanically Durable Asymmetric Supercapacitor Based on NiCo‐Layered Double Hydroxide and Nitrogen‐Doped Graphene Using a Simple Fabrication Method

Abstract

A high‐performing, lightweight, and flexible asymmetric supercapacitor (ASC) using NiCo‐layered double hydroxide (NiCo LDH) supported on 3D nitrogen‐doped graphene (NG) as a positive electrode and NG as a negative electrode is demonstrated. Highly conductive NG provides fast electron transfer and facilitates (dis)charging of NiCo LDH deposited on it. The composite electrode of NiCo LDH@NG exhibits a high specific capacitance of 1421 F g−1 at 2 A g−1. Moreover, the as‐obtained hybrid electrode shows an excellent rate capability with a specific capacitance of 1397 F g−1 at a high current density of 10 A g−1, which is about 98% of the capacitance obtained at 2 A g−1. The flexible ASC device shows a specific capacitance of 109 F g−1 at 0.5 A g−1 and a maximum energy density of 49 W h kg−1, which is comparable with or superior to previously reported electrodes based on nickel‐cobalt hydroxides. Furthermore, an excellent mechanical stability is obtained. Under repeated mechanical bendings, the ASC demonstrates high bending stability up to 450 bending cycles at a 90° angle. Hence, this flexible NiCo LDH@NG electrode that is free of binders and conductive agents shows superior performance and stability, and is a promising candidate for the future wearable energy storage devices.

Mesoporous Nanohybrids of 2D Ni‐Cr‐Layered Double Hydroxide Nanosheets Pillared with Polyoxovanadate Anions for High‐Performance Hybrid Supercapacitor

“…[ 1,21–25 ] The performance of recently reported LDHs and their hybrids as HSC cathodes are summarized, as shown in Figure . [ 21–39 ]…”

Construction of Ce-Doped NiCo-LDH@CNT Nanocomposite Electrodes for High-Performance Supercapacitor Application

“…While three-dimensional (3D) CNT structures have benefits beyond 2D carbon derivatives, for example, 3D electron transportation passageway, excellent conductivity, and hierarchically pore networks, all of these advantages are necessary to improve the performance of catalysts and SCs . Cerium is a component of the lanthanide group with high electrical conductivity and is suitable for preparing water-splitting catalysts and SC in an alkaline environment. − Also, water splitting improved upon Ce doping in LDH structures and growth on CNT skeletons. ,, Co and Ni are applied for the improvement of composite’s electron conductivity and active site density. − The problem of these metal oxides is structural degradation and weak conductivity, which leads to a decline in the electrochemical activity of the composite. Nevertheless, a significant power density, particularly energy density, can be accomplished by making up a composite asymmetric SC in the alkaline condition. , …”

Metal‐organic framework‐derived carbon‐cobalt oxysulfide nanocage heterostructure electrode for efficient hybrid supercapacitors

“…18 Among these, transition metal sulfides have been investigated as active electrode materials for supercapacitors owing to their excellent electrical conductivities compared with their corresponding oxide counterparts. 19 In recent years, mixed or ternary nanostructures with two different cations, such as NiCo-LDH, 20 NiS 2 /ZnS, 21 CoNiS 2 , 22 Co 3 S 4 /NiS, 23 and NiCoS 2 , 24 have exhibited superior electrical and electrochemical characteristics than their single-cation counterparts because of the rich possibilities for reversible redox reactions. Considering the advantages on cationic substitution, understanding the effect on anionic substitution has attracted its benefits upon the electrochemical activities of transition metal ions.…”