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

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. Herein reported is the two step fabrication of a novel electrode; first, nitrogen‐doped graphene is sprayed onto the carbon cloth (NG/CC) and then NiCo‐layered double hydroxide (NiCo LDH) is deposited onto NG/CC (NiCo LDH@NG/CC). An asymmetric supercapacitor is fabricated using NG/CC as a negative electrode and NiCo LDH as a positive electrode. This device is flexible and shows excellent durability under several hundred cycles of mechanical bending.