High-performance hybrid microsupercapacitors based on Co–Mn layered double hydroxide nanosheets

Design and Fabrication of MoCuOx Bimetallic Oxide Electrodes for High-Performance Micro-Supercapacitor by Electro-Spark Machining

Transition metal oxides, distinguished by their high theoretical specific capacitance values, inexpensive cost, and low toxicity, have been extensively utilized as electrode materials for high-performance supercapacitors. Nevertheless, their conductivity is generally insufficient to facilitate rapid electron transport at high rates. Therefore, research on bimetallic oxide electrode materials has become a hot spot, especially in the field of micro-supercapacitors (MSC). Hence, this study presents the preparation of bimetallic oxide electrode materials via electro-spark machining (EM), which is efficient, convenient, green and non-polluting, as well as customizable. The fabricated copper-molybdenum bimetallic oxide (MoCuOx) device showed good electrochemical performance under the electrode system. It provided a high areal capacity of 50.2 mF cm-2 (scan rate: 2 mV s-1) with outstanding cycling retention of 94.9% even after 2000 cycles. This work opens a new window for fabricating bimetallic oxide materials in an efficient, environmental and customizable way for various electronics applications.

Emerging carbonate anion intercalated- ZnCr-layered double hydroxide/vanadium carbide nanocomposite: Sustainable design strategies based on disposal electrochemical sensor for diethofencarb fungicide monitoring

Diethofencarb (DFC) is widely used in agriculture to fight against plant fungal attacks and enhance food crop production. On the other hand, the National food safety standard has set the overall maximum residual limit (MRL) of DFC to be 1 mg/kg. Hence it becomes essential to limit their usage, and it is vital to quantify the amount of DFC present in real-life samples to safeguard the health and environmental well-being. Here, we introduce a simple hydrothermal procedure for preparing vanadium carbide (VC) anchored by ZnCr-LDH. The sustainably designed electrochemical sensor for the detection of DFC portrayed high electro-active surface area, conductivity, rapid-electron transport ratio, and high ion diffusion parameters. The obtained structural and morphological information confirms the enriched electrochemical activity of the ZnCr-LDH/VC/SPCE towards DFC. The ZnCr-LDH/VC/SPCE electrode has displayed exceptional characteristics with DPV resulting in a vast linear response (0.01-228 μM), and lower LOD (2 nM) with high sensitivity. Real-sample analysis was carried out to demonstrate the specificity of the electrode with an acceptable recovery in both water (±98.75-99.70%) and tomato (±98.00-99.75%) samples.

Formation of a CoMn-Layered Double Hydroxide/Graphite Supercapacitor by a Single Electrochemical Step

Hybrid electric storage systems that combine capacitive and faradaic materials need to be well designed to benefit from the advantages of batteries and supercapacitors. The ultimate capacitive material is graphite (GR), yet high capacitance is usually not achieved due to restacking of its sheets. Therefore, an appealing approach to achieve high power and energy systems is to embed a faradaic 2D material in between the graphite sheets. Here, a simple one-step approach was developed, whereby a faradaic material [layered double hydroxide (LDH)] was electrochemically formed inside electrochemically exfoliated graphite. Specifically, GR was exfoliated under negative potentials by CoII and, in the presence of MnII , formed GR-CoMn-LDH, which exhibited a high areal capacitance and energy density. The high areal capacitance was attributed to the exfoliation of the graphite at very negative potentials to form a 3D foam-like structure driven by hydrogen evolution as well as the deposition of CoMn-LDH due to hydroxide ion generation inside the GR sheets. The ratio between the CoII and MnII in the CoMn-LDH was optimized and analyzed, and the electrochemical performance was studied. Analysis of a cross-section of the GR-CoMn-LDH confirmed the deposition of LDH inside the GR layers. The areal capacitance of the electrode was 186 mF cm-2 at a scan rate of 2 mV s-1 . Finally, an asymmetric supercapacitor was assembled with GR-CoMn-LDH and exfoliated graphite as the positive and negative electrodes, respectively, yielding an energy density of 96.1 μWh cm-3 and a power density of 5 mW cm-3 .

Oxygen-defect-rich 3D porous cobalt-gallium layered double hydroxide for high-performance supercapacitor application

In this work, oxygen-defect-rich, three-dimensional (3D) cobalt-gallium layered double hydroxides (Co_0.50-Ga_0.50-LDH) assembled by porous and ultrathin nanosheets are prepared by a simple one-step strategy. Briefly, an aqueous solution containing Co²⁺ and Ga³⁺ is quickly pouring into the aqueous solution of hexamethylenetetramine, the state-of-the-art LDH was obtained followed by a mild and fast hydrothermal reaction. This mild and rapid synthesis strategy introduces a large number of pores into the ultrathin LDH nanosheets, resulting in a high concentration of oxygen vacancies in the Co_0.50-Ga_0.50-LDH, and the concentration of oxygen vacancies can be arbitrarily modulated, which has been corroborated by X-ray photoelectron spectroscopy and electron spin resonance measurements. The synergistic effect of the oxygen vacancy and the introduced Ga ions in the LDH nanosheets enhances the adsorption of the LDH nanosheets on OH^-, endowing Co_0.50-Ga_0.50-LDH with outstanding performance for the supercapacitor application. Co_0.50-Ga_0.50-LDH offers a high specific capacity (0.62C·cm^-2) at 10 mV·s^-1 and extraordinary cycling stability. An aqueous asymmetric supercapacitor (ASC) constructed with Co_0.50-Ga_0.50-LDH and activated carbon (AC) materials exhibits high energy density and a long lifespan. This result encourages the wide application of porous ultrathin LDH nanosheets in energy storage, catalysis and light response.

Electrochemical study on nickel aluminum layered double hydroxides as high-performance electrode material for lithium-ion batteries based on sodium alginate binder

Nickel aluminum layered double hydroxide (NiAl LDH) with nitrate in its interlayer is investigated as a negative electrode material for lithium-ion batteries (LIBs). The effect of the potential range (i.e., 0.01–3.0 V and 0.4–3.0 V vs. Li+/Li) and of the binder on the performance of the material is investigated in 1 M LiPF6 in EC/DMC vs. Li. The NiAl LDH electrode based on sodium alginate (SA) binder shows a high initial discharge specific capacity of 2586 mAh g−1 at 0.05 A g−1 and good stability in the potential range of 0.01–3.0 V vs. Li+/Li, which is better than what obtained with a polyvinylidene difluoride (PVDF)-based electrode. The NiAl LDH electrode with SA binder shows, after 400 cycles at 0.5 A g−1, a cycling retention of 42.2% with a capacity of 697 mAh g−1 and at a high current density of 1.0 A g−1 shows a retention of 27.6% with a capacity of 388 mAh g−1 over 1400 cycles. In the same conditions, the PVDF-based electrode retains only 15.6% with a capacity of 182 mAh g−1 and 8.5% with a capacity of 121 mAh g−1, respectively. Ex situ X-ray photoelectron spectroscopy (XPS) and ex situ X-ray absorption spectroscopy (XAS) reveal a conversion reaction mechanism during Li+ insertion into the NiAl LDH material. X-ray diffraction (XRD) and XPS have been combined with the electrochemical study to understand the effect of different cutoff potentials on the Li-ion storage mechanism.

Graphical abstract

The as-prepared NiAl-NO3−-LDH with the rhombohedral R-3 m space group is investigated as a negative electrode material for lithium-ion batteries (LIBs). The effect of the potential range (i.e., 0.01–3.0 V and 0.4–3.0 V vs. Li+/Li) and of the binder on the material’s performance is investigated in 1 M LiPF6 in EC/DMC vs. Li. Ex situ X-ray photoelectron spectroscopy (XPS) and ex situ X-ray absorption spectroscopy (XAS) reveal a conversion reaction mechanism during Li+ insertion into the NiAl LDH material. X-ray diffraction (XRD) and XPS have been combined with the electrochemical study to understand the effect of different cutoff potentials on the Li-ion storage mechanism. This work highlights the possibility of the direct application of NiAl LDH materials as negative electrodes for LIBs.

Effect of Binding Affinity of Crystal Water on the Electrochemical Performance of Layered Double Hydroxides

The ever-increasing demand for safe batteries has driven research efforts to develop aqueous rechargeable batteries. In this regard, Ni-based layered double hydroxides (LDHs) have received marked attention owing to their adequate operating potential, high specific capacity, and decent cycling performance. Nevertheless, the effect of immobile intercalants (e. g., crystal water and anions) that are inherently present in the interlayer galleries is barely understood. In this paper, we report that the electrochemical performance of LDH largely depends on the extent to which the crystallinity is affected by the binding strength of crystal water to the transition metal slabs. A series of infrared spectroscopy and in-situ X-ray absorption analyses reveal that the lattice disordering in LDHs is beneficial for accommodating the stress during the (de)intercalation of carrier ions, which serves as the origin of their superior specific capacities and cycle life. This study presents a useful structure-property relationship of the way in which the binding affinity of crystal water affects the key electrochemical properties of the host electrode materials.