High-performance Solid-state Hybrid Energy-storage Device Consisting of Reduced Graphene-Oxide Anchored with NiMn-Layered Double Hydroxide

Enhanced Electrochemical Performance of NiMn Layered Double Hydroxides/Graphene Oxide Composites Synthesized by One-Step Hydrothermal Method for Supercapacitors

This study aims to enhance the performance of supercapacitors, focusing particularly on optimizing electrode materials. While pure NiMn layered double hydroxides (LDHs) exhibit excellent electrochemical properties, they have limitations in achieving high specific capacitance. Therefore, this paper successfully synthesized composite materials of NiMn LDHs with varying loadings of graphene oxide (GO) using a hydrothermal method. Systematic physicochemical characterization of the synthesized materials, such as powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), and Raman spectroscopy, revealed the influence of GO doping on the microstructure and electrochemical performance of NiMn LDHs. Electrochemical tests demonstrated that the NiMn LDHs/GO electrode material exhibited optimal electrochemical performance with a specific capacitance of 2096 F g-1 at 1 A g-1 current density and 1471 F g-1 at 10 A g-1, when GO doping level was 0.45 wt %. Furthermore, after 1000 cycles of stability testing, the material retained 53.3 % capacitance at 5 A g-1, indicating good cyclic stability. This study not only provides new directions for research on supercapacitor electrode materials but also offers new strategies for developing low-cost and efficient electrode materials.

Etching-induced ion exchange engineering of two-dimensional layered NiFeCo-based hydroxides for high energy charge storage

Efficient and rapid synthesis of transition metal-based hydroxides with tailored microstructures has emerged as a promising approach to fabricate high-performance electrode materials for energy storage devices. However, many conventional synthesis methods are cumbersome, expensive and time-consuming, and the microstructures of electrode materials are usually uncontrollable. Herein, we propose a fast and cost-effective approach to electrochemically in situ grow NiFeCo-based ternary hydroxides (NiFeCo-THs) with layered nanosheet structures on pretreated nickel foam (NF). The in situ grown NiFeCo-THs were in direct contact with the NF to form a monolithic electrode as NiFeCo/NF. By engineering the ion exchange process for controlling the ionic ratio, the monolithic Ni1(Fe/Co = 1/1)0.5/NF electrode was fabricated and found to show the optimum electrochemical behavior with a specific capacitance of 2.32 C cm-2 at 2 mA cm-2 as a result of its characteristic microstructures. Furthermore, a hybrid supercapacitor was constructed utilizing the monolithic Ni1(Fe/Co = 1/1)0.5/NF electrode and activated carbon as the cathode and anode, respectively, and it was found to have an energy density of 81.1 μW h cm-2 at a power density of 808.8 μW cm-2. After 5000 cycles, 84.0% of the initial capacitance of the hybrid supercapacitor was maintained, and the monolithic Ni1(Fe/Co = 1/1)0.5/NF electrode still retained the arrayed nanosheet structure.

Mg doping of NiMn-LDH with a three-dimensional porous morphology for an efficient supercapacitor

As a promising supercapacitor electrode material, NiMn-LDH has attracted great attention due to its high theoretical capacity and easy preparation. However, the development and application of NiMn-LDH in supercapacitors are limited because of its poor cycling stability and low electrical conductivity. To solve these problems, a NiMnMg-LDH with a three-dimensional porous morphology has been successfully fabricated by doping with Mg to improve its electrochemical properties. Experimental results indicate that NiMnMg-LDH-7 delivers a specific capacitance of 1772 F g^-1 at a current density of 1 A g^-1. Moreover, it can still reach 1080 F g^-1 when the current density is increased 10 times, suggesting excellent rate capability. The asymmetric supercapacitor (ASC) NiMnMg-LDH-7//AC can provide a high energy density of 28 W h kg^-1 at a power density of 700 W kg^-1. Furthermore, the energy density can still reach 16 W h kg^-1 even if the power density is increased to close to 3500 W kg^-1. The capacity retention of this ASC device can reach 74% after 3000 cycles at a current density of 3 A g^-1. These excellent properties of NiMnMg-LDH can be attributed to the obvious improvement of its specific surface area and electrical conductivity owing to doping with the element magnesium. We believe that this work could provide a new idea for the preparation of high-performance electrode materials for supercapacitors.

Spatially Confined Li Growth on Honeycomb-like Lithiophilic Layered Double Hydroxide Nanosheet Arrays toward a Stable Li Metal Anode

A lithium metal anode (LMA) is appealing due to its high theoretical capacity and low electrochemical potential. Unfortunately, the practical application of LMAs is restricted by the uncontrollable Li dendrite growth and tremendous volume change. Herein, lithiophilic honeycomb-like layered double hydroxide (LDH) nanosheet arrays supported on a flexible carbon cloth (NiMn-LDHs NAs@CC) are synthesized as the Li host to spatially confine the Li deposition, guiding Li growth via a conformal and uniform manner. First, the lithiophilic NiMn-LDHs NAs as nucleation seeds render the CC substance outstanding lithiophilicity and reduce the nucleation barrier. The hierarchical honeycomb-like structure then directs the oriented Li deposition and provides an open channel for fast ion transport. Finally, the CC skeleton offers a high specific surface for decreasing the inhomogeneous distribution of the current density and enough space for alleviating the volume variations, synergistically inhibiting the dendritic Li growth. As a consequence, the NiMn-LDHs NAs@CC symmetric cell exhibits a low overpotential of less than 17 mV at 2 mA cm^-2 and a long lifespan of 2100 h at 3 mA cm^-2. In addition, when paired with the LiNiCoMnO₂ (NCM111) cathode, the NiMn-LDHs NAs@CC@Li full cell presents enhanced cycling stability and rate capability in comparison to the CC@Li full cell, implying the great potential of the NiMn-LDHs NAs@CC in stabilizing the LMA.

Performance of sodium-ion supercapattery using LaMnO3 and rGO in non-aqueous electrolyte

Hydrothermally-derived LaMnO3 as an electrode material for a sodium and lithium ion supercapattery.

High performance asymmetric supercapacitor based on vertical nanowire arrays of a novel Ni@Co-Fe LDH core@shell as negative and Ni(OH)2 as positive electrode

An efficient synthesis of the electrode material with abundant active sites is imperative for obtaining a flexible supercapacitor with excellent electrochemical performance. Herein, a novel flexible Ni@Co-Fe LDH core-shell nanowires supercapacitor negative electrode is synthesized using polycarbonate membrane on a copper substrate via an electrochemical deposition technique. The synthesized battery-type negative electrode exhibits remarkable specific capacitance of 1289 F g^-1 at 1 A g^-1 and excellent cycling stability with 76.66% capacitive retention after 5000 cycles. Furthermore, the Ni(OH)₂//Ni@Co-Fe LDH nanowires based asymmetric supercapacitor exhibits excellent cycling stability of 90.49% after 1000 cycles with a highest energy density of 68 Wh kg^-1 at 0.38 KW kg^-1, and a good energy density of 31.8 Wh kg^-1 is still attained at a high power density of 6 KW kg^-1. For practical demonstration, a white LED of 3.3 V is lit by using two asymmetrical supercapacitor devices connected in series. The device offers a favorable and effective pathway for advanced energy storage.

Surface Engineering of Graphene Oxide Shells Using Lamellar LDH Nanostructures

The discovery of graphene oxide (GO) has made a profound impact on varied areas of research due to its excellent physicochemical properties. However, surface engineering of these nanostructures holds the key to enhanced surface properties. Here, we introduce surface engineering of reduced GO (rGO) shells by radially grafting Ni-Co layered double hydroxide (LDH) lamella on rGO shells to form Ni-Co LDH@rGO. The morphology of synthesized Ni-Co LDH@rGO mimics dendritic cell-like three-dimensional (3D) hierarchical morphologies. Silica nanospheres form self-sacrificial templates during the reduction of GO shells to form rGO shells during the template-assisted synthesis. The radial growth of LDH lamellae during hydrothermal process on GO shells provides access to a significantly larger number of additional active redox sites and overcompensates the loss of pseudocapacitive charge storage centers during the reduction of GO to form rGO shells. This enables in the synthesis of novel surface-engineered rGO nanoshells, which provide large surface area, enhanced redox sites, high porosity, and easy transport of ions. These synthesized 3D dendritic cell-like morphologies of Ni-Co LDH@rGO show a high capacitance of ∼2640 F g^-1. A flexible hybrid device fabricated using this nanomaterial shows a high energy density of ∼35 Wh kg^-1 and a power density of 750 W kg^-1 at 1 A g^-1. No appreciable compromise in device performance is observed under bending conditions. This synthesis strategy may be used in the development of functional materials useful for potential applications, including sensors, catalysts, and energy storage.

Interlaced NiMn-LDH nanosheet decorated NiCo2O4 nanowire arrays on carbon cloth as advanced electrodes for high-performance flexible solid-state hybrid supercapacitors

3D hierarchical NiCo₂O₄@NiMn-LDH nanowire/nanosheet arrays have been successfully fabricated on carbon cloth as superior battery-type electrode for high-performance flexible solid-state HSC devices.

Research Progress of NiMn Layered Double Hydroxides for Supercapacitors: A Review

The research on supercapacitors has been attractive due to their large power density, fast charge/discharge speed and long lifespan. The electrode materials for supercapacitors are thus intensively investigated to improve the electrochemical performances. Various transition metal layered double hydroxides (LDHs) with a hydrotalcite-like structure have been developed to be promising electrode materials. Earth-abundant metal hydroxides are very suitable electrode materials due to the low cost and high specific capacity. This is a review paper on NiMn LDHs for supercapacitor application. We focus particularly on the recent published papers using NiMn LDHs as electrode materials for supercapacitors. The preparation methods for NiMn LDHs are introduced first. Then, the structural design and chemical modification of NiMn LDH materials, as well as the composites and films derived from NiMn LDHs are discussed. These approaches are proven to be effective to enhance the performance of supercapacitor. Finally, the reports related to NiMn LDH-based asymmetric supercapacitors are summarized. A brief discussion of the future development of NiMn LDHs is also provided.

Ni–Co layered double hydroxide on carbon nanorods and graphene nanoribbons derived from MOFs for supercapacitors

In this study, carbon nanorods (CNR) and graphene nanoribbons (GNR) derived from metal–organic frameworks (MOFs) were first prepared by solvothermal method.

Polyhedral-Like NiMn-Layered Double Hydroxide/Porous Carbon as Electrode for Enhanced Electrochemical Performance Supercapacitors

Polyhedral-like NiMn-layered double hydroxide/porous carbon (NiMn-LDH/PC-x) composites are successfully synthesized by hydrothermal method (x = 1, 2 means different mass percent of porous carbon (PC) in composites). The NiMn-LDH/PC-1 composites possess specific capacitance 1634 F g^-1 at a current density of 1 A g^-1 , and it is much better than that of pure LDH (1095 F g^-1 at 1 A g^-1 ). Besides, the sample can retain 84.58% of original capacitance after 3000 cycles at 15 A g^-1 . An asymmetric supercapacitor with NiMn-LDH/PC-1 as anode and activated carbon as cathode is fabricated, and the supercapacitor can achieve an energy density of 18.60 Wh kg^-1 at a power density of 225.03 W kg^-1 . The enhanced electrochemical performance attributes to the high faradaic pseudocapacitance of NiMn-LDH, the introduction of PC, and the 3D porous structure of LDH/PC-1 composites. The introduction of PC hinders serious agglomeration of LDH and further accelerates ions transport. The encouraging results indicate that these materials are one of the most potential candidates for energy storage devices.