Electrochemical performance of 3D porous Ni-Co oxide with electrochemically exfoliated graphene for asymmetric supercapacitor applications

Cu2S/C@NiMnCe-layered double hydroxide with core-shell rods array structure as the cathode for high performance supercapacitors

The selection of highly efficient materials and the construction of advantageous structures are essential for realizing high-performance electrode materials. In this paper, electrode material Cu2S/C@NiMnCe-LDH/CF with excellent morphology and high performance has been successfully designed and prepared by simple hydrothermal and calcination techniques. First, ZIF-67 is loaded on the outer layer of Cu2S rods to obtain core-shell structured Cu2S@ZIF-67 rods, whose ZIF-67 MOF shell is carbonized to obtain Cu2S@C rods. Then, NiMnCe-LDH are epitaxially loaded on the outer layer of Cu2S@C to obtain Cu2S/C@NiMnCe-LDH rods. At a current density of 2 mA cm-2, Cu2S/C@NiMnCe-LDH/CF exhibits an area capacitance of 5176.4 mF cm-2. The mass capacitance and the energy density of the Cu2S/C@NiMnCe-LDH/CF//AC asymmetric supercapacitor (ASC) reach 150.82F g-1 at a sweep rate of 0.8 A/g and 53.62 Wh kg-1 at a power density of 639.99 W kg-1, respectively. Meanwhile, after 8000 electrochemical cycles, the specific capacitance of Cu2S/C@NiMnCe-LDH/CF//AC still has a retention rate of 86.32 %, which proves its excellent cycling stability. These results demonstrate a new strategy for the preparation of novel core-shell structured Cu2S/C@NiMnCe-LDH/CF nanocomposite material for electrode materials of energy storage devices with superb performance.

Recent Progress in Two-Dimensional Layered Double Hydroxides and Their Derivatives for Supercapacitors

High-performance supercapacitors have attracted great attention due to their high power, fast charging/discharging, long lifetime, and high safety. However, the generally low energy density and overall device performance of supercapacitors limit their applications. In recent years, the design of rational electrode materials has proven to be an effective pathway to improve the capacitive performances of supercapacitors. Layered double hydroxides (LDHs), have shown great potential in new-generation supercapacitors, due to their unique two-dimensional layered structures with a high surface area and tunable composition of the host layers and intercalation species. Herein, recent progress in LDH-based, LDH-derived, and composite-type electrode materials targeted for applications in supercapacitors, by tuning the chemical/metal composition, growth morphology, architectures, and device integration, is reviewed. The complicated relationships between the composition, morphology, structure, and capacitive performance are presented. A brief projection is given for the challenges and perspectives of LDHs for energy research.

Three-Dimensional Core-Branch α-Fe2O3@NiO/Carbon Cloth Heterostructured Electrodes for Flexible Supercapacitors

A convenient and scalable hydrothermal method was developed for the fabrication of the core-branch Fe₂O₃@NiO nanorods arrays directly grown on flexible carbon cloth (denoted as Fe₂O₃@NiO/CC). Such a unique architecture was applied as an electrode of the supercapacitors. As a result, the Fe₂O₃@NiO/CC exhibited a high areal capacitance ~800 mF cm^-2 at 10 mA cm^-2, which was about 10 times increase with respect to Fe₂O₃ nanorods array grown on carbon cloth (Fe₂O₃/CC). The Fe₂O₃@NiO/CC also had the long life cycle (96.8 % capacitance retention after 16,000 cycles) and remarkable rate capability (44.0 % capacitance loss at a very large current density of 100 mA cm^-2). The superior performance of the Fe₂O₃@NiO/CC should be ascribed to the reduction of the contact resistance and the free-standing structure of the flexible electrode. This study provides a novel strategy to construct high-performance flexible electrode materials with unique core-branch structure by incorporating two different pseudocapacitive materials.