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The effective integration of nanomaterials with underlying current collectors is a key factor affecting the performance of nonenzymatic glucose sensors, where an inappropriate integration structure often leads to poor electron transport and instability. In this work, a seamless integrated electrode was constructed by the in situ immobilizing of a nickel-based metal-organic framework (Ni-MOF) on a three-dimensional (3D) conductive nickel foam (NF) for highly sensitive and durable glucose sensing. Facilitated by a rapid microwave-assisted reaction, a robust interfacial interaction between the Ni-MOF and the substrate was established through in situ conversion from nickel oxide (NiO). The fabricated Ni-MOF/NF electrode exhibits an excellent limit of detection (LOD) of 2.65 μM and an impressive sensitivity (14.31 mA cm-2 mM-1) within the linear range (4-576 μM), which is significantly boosted compared with that of an electrode prepared by a typical drop-casting method (3.56 mA cm-2 mM-1 in 4-1836 μM). Characterization and electrochemical tests reveal that this integrated structure on the one hand contributes to fast electron transport and thus has enhanced sensitivity and on the other hand leads to exceptional durability with its structural integrity maintained under bending, shaking, and ultrasonication. Moreover, this seamless integration method was also employed to immobilize the Ni-MOF converted from the pre-chemically deposited NiO layer on another type of substrate, 3D carbon paper (CP), demonstrating the versatility of this facile strategy in creating diverse electrochemical electrodes for applications beyond glucose sensing. [ABSTRACT FROM AUTHOR]

Heterogeneous interface construction is of far-reaching significance to optimize the electrochemical performance of electrodes. Herein, a multi-step alternating electrochemical deposition (MAED) method is proposed to alternately deposit Co0.85Se and Ni3S4 nanosheets on a nickel foam (NF), forming a special alternate layer-by-layer structure with multi-layered heterogeneous interfaces. The creation of the multi-layered heterogeneous interfaces provides a large interfacial area for redox reactions with optimum interstitials facilitating ion diffusion, thus greatly improving the electrochemical energy storage efficiency. With the increase in the layer number, the material exhibits increasingly better energy storage performance, and 8L-Co0.85Se@Ni3S4/NF exhibits the highest specific capacitances of 2508 F g−1 and 1558 F g−1 at a scan rate of 2 mV s−1 and a current density of 1 A g−1. The 8L-Co0.85Se@Ni3S4/NF//polypyrrole (PPy)/NF asymmetric supercapacitor provides a maximum operation potential window of 1.55 V and energy densities of 76.98 and 35.74 W h kg−1 when the power densities are 775.0 and 15 500 W kg−1, respectively, superior to most of the related materials reported. Through MAED, the deposited phase and the layer number can be accurately controlled, thus providing an efficient strategy for interface construction so as to increase the electrochemical activity of the energy storage materials. [ABSTRACT FROM AUTHOR]

Exploring new strategies to design non-precious and efficient electrocatalysts can provide a solution for sluggish electrocatalytic kinetics and sustainable hydrogen energy. Transition metal selenides are potential contenders for bifunctional electrocatalysis owing to their unique layered structure, low band gap, and high intrinsic activities. However, insufficient access to active sites, lethargic water dissociation, and structural degradation of active materials during electrochemical reactions limit their activities, especially in alkaline media. In this article, we report a useful strategy to assemble vanadium diselenide (VSe2) into a 3D MXene/rGO-based sponge-like architecture (VSe2@G/MXe) using hydrothermal and freeze-drying approaches. The 3D hierarchical meso/macro-pore rich sponge-like morphology not only prevents aggregation of VSe2 nanosheets but also offers a kinetics-favorable framework and high robustness to the electrocatalyst. Synergistic coupling of VSe2 and a MXene/rGO matrix yields a heterostructure with a large specific surface area, high conductivity, and multi-dimensional anisotropic pore channels for uninterrupted mass transport and gas diffusion. Consequently, VSe2@G/MXe presented superior electrochemical activity for both the HER and OER compared to its counterparts (VSe2 and VSe2@G), in alkaline media. The overpotentials required to reach a cathodic and anodic current density of 10 mA cm−2 were 153 mV (Tafel slope = 84 mV dec−1) and 241 mV (Tafel slope = 87 mV dec−1), respectively. The Rct values at the open circuit voltage were as low as 9.1 Ω and 1.41 Ω for the HER and OER activity, respectively. Importantly, VSe2@G/MXe withstands a steady current output for a long 24 h operating time. Hence, this work presents a rational design for 3D microstructures with optimum characteristics for efficient bifunctional alkaline water-splitting. [ABSTRACT FROM AUTHOR]

Doping engineering is an effective modification strategy to enhance the electrochemical performance of electrode materials. In this paper, the impacts of heteroatom doping in monolayer titanium disulfide (TiS2) by substituting the S atom with the heteroatoms (B, C, N, O, F, and P) on the adsorption and diffusion capabilities of alkali metals (Li, Na, and K) have been systematically investigated using first-principles calculations to evaluate the material performance for application in alkali metal-ion batteries. The doping of most heteroatoms can promote the adsorption capability of alkali metal atoms on monolayer TiS2 as their adsorption energies decrease compared with the pristine system, particularly for p-type doping with C, N, and P. The diffusion energy barriers decrease when alkali metals approach the doping site of most heteroatom-doped TiS2, and the barriers near the doping site are extremely small (0.00–0.08 eV), whereas they slightly increase as alkali metals move away from the doping site. P doping has the lowest overall diffusion energy barrier for each metal. Thus, monolayer TiS2 with heteroatom doping, especially P doping, can be used as a potential anode material for alkali metal-ion batteries. This study can help comprehend the impacts of heteroatom doping and design high-performance electrode materials for rechargeable batteries. [ABSTRACT FROM AUTHOR]

In this work, nickel-catecholate (Ni-CAT) nanorods were in situ compounded on graphene oxide (GO) to form a composite Ni-CAT@GO (NCG) with a special "blanket-shape" structure, which was used as an electrode material for supercapacitors. The morphology of Ni-CATs in situ grown on GO was modulated by introducing various contents of GO. With increasing GO, the length of nanorods of Ni-CATs is obviously shortened, and the charge transfer resistance of NCG is significantly reduced as the GO content is relatively low while it increases with further addition of GO, because excessive GO in NCG results in smaller crystal sizes accompanied by smaller stacking pores. Both the over-long Ni-CAT nanorods and the smaller stacking pores can restrict the accessible surface areas for the electrolyte. Optimal nanorod sizes are crucial to achieve good electrochemical performance for electrode materials. Galvanostatic charge–discharge analysis of NCG electrodes shows that their capacity initially increases and then decreases with the addition of more and more GO, and Ni-CAT@GO-0.5 (NCG0.5) with minimal charge transfer resistance exhibits the best electrochemical performance. The results demonstrate that the NCG0.5 electrode with optimal morphology possesses an excellent capacitance of 563.8 F g−1 at 0.5 A g−1 and a good rate performance of 61.9% at 10 A g−1, indicating that Ni-CAT@GO is a new type of promising electrode material for supercapacitors based on conductive metal–organic frameworks. [ABSTRACT FROM AUTHOR]

The development prospects of conventional Li-ion batteries are limited by the paucity of Li resources. Mg–Li hybrid batteries (MLIBs) combine the advantages of Li-ion batteries and magnesium batteries. Li+ can migrate rapidly in the cathode materials, and the Mg anode has the advantage of being dendrite-free. In this study, a type of Li4Ti5O12 composite material doped with Sn4+ and a conductive carbon skeleton (Li4Ti4.9Sn0.1O12/C, Sn0.1-LTO/C) was prepared by a simple one-pot sol–gel method. The doped Sn4+ replaces part of Ti4+ in the crystal lattice, which makes Ti3+ require charge compensation, thus improving the ionic conductivity. The intervention of the conductive carbon skeleton further improves the conductivity of the Sn0.1-LTO/C composite material. The performance of Sn0.1-LTO/C as the cathode of MLIBs is explored. The initial discharge capacity was 159.1 mA h g−1 at 0.5 C, and it was maintained at 105 mA h g−1 even after 500 cycles. The excellent electrochemical performance is attributed to a small amount of Sn doping and the involvement of the conductive carbon skeleton, which indicated that the Sn0.1-LTO/C composite material provides great potential application in MLIBs. [ABSTRACT FROM AUTHOR]

Developing eco-friendly and low-cost advanced anode materials, such as Fe2O3 and Mn3O4, is fundamental to improve the electrochemical performance of lithium-ion batteries (LIBs). The rational engineering of the microstructure of Fe2O3 and Mn3O4 to endow it with one-dimensionally and hierarchically porous architecture is a feasible way to further improve and optimize the electrochemical performance of the anode materials. Herein, we demonstrate a facile strategy to prepare nanotubular Fe2O3 and Mn3O4 as advanced anode materials for high-performance LIBs. By combining the merits of the one-dimensionally nanotubular morphology and hierarchically porous structure, limitations in the lithiation activity of Mn3O4 and Fe2O3 anode materials, such as low electrical conductivity, large volume expansion, and sluggish lithium-ion diffusion within the materials, have been effectively overcome. When used as anode materials, t-Fe2O3 and t-Mn3O4 exhibited outstanding electrochemical performances, including a high reversible discharge capacity (859.7 and 901.4 mA h g−1 for t-Fe2O3 and t-Mn3O4, respectively), excellent rate performance, and ultra-stable cycling stability. Such superior electrochemical performances proved the exceptional potential of the materials for the real-world application in LIBs. [ABSTRACT FROM AUTHOR]

The Ni-rich layered oxide cathode has shown high energy density, proper rate capability, and longevity of the rechargeable battery, while poor stability and capacity fading are assumed to be its common cons. To address this obstacle, prospective cathode materials are synthesized by integrating the lithium transition metal oxides with an artificial cathode electrolyte interphase (CEI) layer. Herein, plasma-enhanced atomic layer deposition (PEALD) is employed to coat the LiNi0.8Mn0.1Co0.1O2 (NMC811) electrode with Al2O3 and MoO3. The combined results from morphological examinations revealed the formation of uniform Al2O3 and MoO3 sheets after 200 cycles of PEALD coating. Consistent results from the XRD analysis demonstrate that Al2O3 and MoO3 artificial CEIs can reduce Li–Ni mixing. The cyclic voltammetry tests show the oxidation–reduction kinetic. The modified NMC811 structures with Al2O3 and MoO3 represent a remarkable improvement in terms of capacity retention. The coated cathode with Al2O3 clearly outperforms the modified configuration with MoO3 concerning ionic conductivity, charge/discharge reversibility, and capacity retention. The promising results obtained in this study open the possibility of synthesizing Ni-rich cathodes with enhanced electrochemical performance. [ABSTRACT FROM AUTHOR]

Transition metal sulfides have broad application prospects as supercapacitor electrode materials. However, their poor structural stability and conductivity hinder improvements in their electrochemical performance. Therefore, the introduction of highly conductive carbon nanotubes (CNTs) as sulfide growth substrates is considered to improve the microstructure and electrochemical performance of electrode materials. In this study, a highly conductive CNT solution was sprayed onto a nickel foam current collector, and Co3S4/Ni0.96S was successfully constructed on a CNT conductive substrate using a combination of hydrothermal and electrochemical deposition methods, forming a unique nanosheet-covered nanotube structure Co3S4/Ni0.96S@CNTs. The addition of an appropriate concentration of CNTs can not only serve as a substrate for the growth of Co3S4/Ni0.96S, but also effectively maintain the overall nanosheet structure. Thus, the Co3S4/Ni0.96S@CNTs (2-CSNS@CNTs) have a stable structure and a wide range of electrochemical reaction sites, ensuring excellent conductivity and cycling stability. The electrode material 2-CSNS@CNTs exhibited a specific capacity of 1427.05 C g−1 at 1 A g−1. Additionally, the asymmetric supercapacitor 2-CSNS@CNTs exhibited a high energy density of 53.76 W h kg−1 at 800 W kg−1 and a capacity retention rate of 68.5% at 10 A g−1 after 1000 cycles. [ABSTRACT FROM AUTHOR]

The transformation from LiNi1−x−yCoxMnyO2 (NCM) cathodes to Co-free LiNi1−xMnxO2 (NM) cathodes is considered as an effective solution for the electric vehicle (EV) industry to deal with the high cost of cobalt. However, severe Li/Ni disorder, structural instability and poor cycling stability are the main obstacles to their practical application. Al doping has proven to be an effective method to improve the electrochemical performance of Ni-rich NCMs. However, with regard to Ni-rich Co-free NM cathodes, the influence of Al doping on the structural stability and electrochemical performance of NM cathodes is still not clear. In this work, Al doped LiNi0.8Mn0.2−xAlxO2 cathodes are designed and their structural stability and electrochemical performance are investigated by a combination of XRD, SEM, TEM, CV, GITT, cycling testing and EIS techniques. As a result, Al doping can effectively inhibit Li/Ni disorder and improve the structural and thermal stability. In detail, 5% is the optimal doping amount for LiNi0.8Mn0.2O2 cathodes to obtain the best electrochemical performance and the LiNi0.8Mn0.15Al0.05O2 cathode shows an excellent capacity retention of 91.97% after 300 cycles at 3.0–4.3 V. This work provides an effective strategy for the development of Ni-rich Co-free NM cathodes. [ABSTRACT FROM AUTHOR]

For obtaining high-performance lithium-ion batteries, it is important to develop new cathode materials with high capacity. Herein, a one-dimensional coordination polymer [Co(4-DTBPT) (DMF)2(H2O)2] (4-DTBPT) (C10H4O8) (Co-DTBPT) (4-DTBPT = 2,7-di(4H-1,2,4-triazol-4yl)benzo[lmn][3,8] phenanthroline-1,3,6,8-(2H,7H)-tetraone; DMF = dimethylformamide) was synthesized and its electrochemical performance as the cathode material of lithium-ion batteries was first investigated. The Co-DTBPT electrode showed better cycling stability and a specific capacity of 55 mA h g−1 at 50 mA g−1 after 50 cycles, and the coulombic efficiency was close to 100%. The capacity contribution of the Co-DTBPT electrode may be ascribed to the redox reaction of the Co(II) ion and the 4-DTBPT ligand in the process of charge and discharge. Our work proves once again that using one-dimensional coordination polymers as cathode materials for lithium-ion batteries is a feasible way. [ABSTRACT FROM AUTHOR]

Currently, the preparation of high-performance electrode materials is urgently needed for supercapacitors. As a new kind of organic porous material, covalent organic frameworks (COFs) with an ordered pore structure, a high specific surface area and designability, have shown great potential application value as electrode materials for supercapacitors. However, their potential application in supercapacitors is limited by the poor conductivity of COFs. Here, we in situ grew the highly crystalline triazine-based covalent organic framework DHTA-COF on a modified -Al2O3 substrate to obtain the composites Al2O3@DHTA-COFs. Some of the obtained Al2O3@DHTA-COF composites can maintain some degree of crystallinity, good stability and a vesicular structure. Compared to the precursors -Al2O3 and DHTA-COF, the 50%Al2O3@DHTA-COF composite has superior electrochemical properties as electrode materials for supercapacitors. Under the same conditions, the specific capacitance values of 50%Al2O3@DHTA-COF (261.5 F g−1 at 0.5 A g−1) are 6.2 and 9.6 times higher than the values of DHTA-COF and -Al2O3–CHO, respectively. Additionally, the 50%Al2O3@DHTA-COF electrode material exhibited long-term cycling stability even after 6000 charge–discharge cycles. The study can provide some reference for the development of COF-based composite materials for energy storage. [ABSTRACT FROM AUTHOR]

Lithium–sulfur (Li–S) batteries have attracted great research attention because of their high energy density and low cost. However, shuttling effects of polysulfides and insulation from elemental sulfur hinder their practical application. Herein, we report hollow carbon nanofibers filled with carbon nanotubes (denoted as HCNF/CNT) as host materials for sulfur to mitigate the shuttling behavior and improve the kinetics of insulative sulfur. The as-prepared HCNF/CNT with nano-conductive domains in the hollow carbon nanofibers enables high loading and efficient utilization of sulfur. Owing to their unique structural superiority, the sulfur-encapsulated HCNF/CNT cathode materials for Li–S batteries deliver excellent electrochemical performance, including high specific capacity of 1156 mA h g−1 at 0.2 C, good rate performance and cycling stability with a capacity retention of 77.2% after 200 cycles at 2 C. Such a unique structure can provide inspiration for the rational structural design of carbon materials as hosts for high performance Li–S batteries. [ABSTRACT FROM AUTHOR]

Transition metal-based binary and ternary compound arrays were directly grown on a porous Ni foam substrate using a facile one-step hydrothermal method. Transition metals are considered ideal electrode materials for faradaic capacitors because they exhibit a wide range of oxidation states enabling effective redox charge transfer. Furthermore, compounds in which two or more transition metals react can help increase the number of active sites for charge–discharge reactions and provide more valence changes for improved charge transfer. In this work, we fabricated ternary electrodes with Ni, Cu, and Zn ions, exhibiting a larger surface area and higher entropy than those made with binary compounds. The NixCuyZnz-based ternary electrode had a shorter diffusion path for the electrolyte ions owing to its larger surface area. Ternary compounds can increase the entropy of the electrode because of the reaction between atoms of different sizes, bringing about a synergistic effect for high characteristic electrochemical values. The optimized Ni x Cu y Zn z (CO3)(OH)2 compound showed a maximum specific capacity of 344 mA h g−1 at a current density of 3 A g−1, which was remarkably higher than that of the binary electrode, and a cycling stability of 84.9% after 5000 cycles. An asymmetric supercapacitor produced with this compound as the positive electrode and graphene as the negative electrode exhibited a high energy density of 36.2 W h kg−1 at a power density of 103.1 W kg−1 and a current density of 2 A g−1. The asymmetric supercapacitor fabricated using the Ni x Cu y Zn z (CO3)(OH)2 compound as the positive electrode exhibited excellent electrical properties when used in an illuminated LED device. [ABSTRACT FROM AUTHOR]

Rational construction of nanosized anode nanomaterials is crucial to enhance the electrochemical performance of lithium-/sodium-ion batteries (LIBs/SIBs). Various anode nanoparticles are created mainly via templating surface confinement, or encapsulation within precursors (such as metal–organic frameworks). Herein, low-content SnO2 nanodots on N-doped reduced graphene oxide (SnO2@N-rGO) were prepared as anode nanomaterials for LIBs and SIBs, via a distinctive lattice confinement of a CoAlSn-layered double hydroxide (CoAlSn-LDH) precursor. The SnO2@N-rGO composite exhibits the advantagous features of low-content (17.9 wt%) and uniform SnO2 nanodots (3.0 ± 0.5 nm) resulting from the lattice confinement of the Co and Al species to the surrounded Sn within the same crystalline layer, and high-content conductive rGO. The SnO2@N-rGO composite delivers a highly reversible capacity of 1146.2 mA h g−1 after 100 cycles at 0.1 A g−1 for LIBs, and 387 mA h g−1 after 100 cycles at 0.1 A g−1 for SIBs, outperforming N-rGO. Furthermore, the dominant capacitive contribution and the rapid electronic and ionic transfer, as well as small volume variation, all give rise to the enhancement. Precursor-based lattice confinement could thus be an effective strategy for designing and preparing uniform nanodots as anode nanomaterials for electrochemical energy storage. [ABSTRACT FROM AUTHOR]

In this paper, two kinds of hybrid α-Fe2O3@Co3O4 and α-Fe2O3@MnCo2O4 composites with high yield have been successfully synthesized on a flexible carbon cloth via simple solution methods. These as-obtained products serve as supercapacitor electrodes without the use of any adscititious surfactants and binders. These two hybrid electrode architectures make full use of the synergistic effects between α-Fe2O3 frameworks and coated Co3O4 or MnCo2O4 layers. They exhibit obviously enhanced discharge areal capacitance of 490 mF cm−2 and 1073 mF cm−2 for α-Fe2O3@Co3O4 and α-Fe2O3@MnCo2O4 composites at 1 mA cm−2 with an identical potential voltage of 0–0.9 V. Long-life cycling stability with capacitance retention of 74.6% for α-Fe2O3@Co3O4 and 77.8% for α-Fe2O3@MnCo2O4 are presented after 6000 charge/discharge cycles, respectively. Such prominent electrochemical performances are mainly ascribed to the hybrid composites, which can provide a large reaction surface area, fast ion and electron transfer and good structure combination stability. The as-synthesized flexible hybrid composites might have promising applications in micro/nanoscale energy storage devices. [ABSTRACT FROM AUTHOR]

LiTMPO4 materials, such as LiNiPO4, can maintain structural stability and Li+ transport activity up to 4.8 V, showing great potential to stabilize layered nickel-rich cathodes at high voltage. But achieving a uniform LiTMPO4 coating layer remains a great challenge. Herein, an ultrathin and uniform LiTMPO4 layer (mainly LiNiPO4) is successfully coated on the surface of LiNi0.8Co0.15Mn0.05O2 (NMC@LTMP) via utilizing the surface chelation of phytic acid with NMC precursors and a subsequent high-temperature in situ reaction. The reconstructed surface and interface could act as stable paths for Li+ transport and efficient barriers against electrolyte corrosion. Thus, harmful side reactions like solid electrolyte interphase overgrowth, irreversible phase transformation, and metal dissolution are inhibited simultaneously. Impressively, the optimized NMC@LTMP2 cathode exhibits remarkably improved capacity, as high as 215 mA h g−1 at 2.8–4.5 V, with capacity retention of 87.21% after 200 cycles and outstanding rate capability of 140 mA h g−1 at 10C, significantly better than a pristine cathode. Furthermore, a pouch cell assembled with an NMC@LTMP2 cathode and graphite anode also exhibits robust capacity retention of 82.42% after 100 cycles. These results provide useful insights towards enabling the application of NMC cathodes via developing facile modification methods. [ABSTRACT FROM AUTHOR]

The Li2MoO3 (LMO) material is one promising cathode material for lithium-ion batteries due to its high specific capacity and absence of oxygen release. However, its surface instability in air and poor conductivity have limited its application. To solve these problems, the Ru element has been successfully introduced into the LMO lattice with the aid of the molten salt method. XRD and TEM characterization showed that the introduction of Ru does not change the crystal structure but expands the crystal plane spacing of the {001} facets, which is further evidenced by density functional theory (DFT) calculations. XPS and EDS tests indicated that the introduction of Ru inhibits the oxidation of Mo species and leads to a more uniform distribution of the material. In addition, DFT calculations revealed that covalent interactions are formed between Mo4d/Ru4d and O2p orbitals, leading to a significant reduction of the band gap. Therefore, Ru-doped samples exhibit good electrochemical performances. The initial discharge capacity of an LMRO-2 sample reaches 299.1 mA h g−1 at a 1C rate, and the capacity remains at 125.2 mA h g−1 after 100 cycles. In comparison, the initial discharge capacity of pure phase sample LMO is only 250.5 mA h g−1 under the same conditions, and the capacity remains only at 76.5 mA h g−1 after 100 cycles. The present results confirmed that Ru doping is an effective strategy to improve the performance of the LMO cathode material. [ABSTRACT FROM AUTHOR]

The core–shell structured CuO@NiCoMn-LDH electrode was synthesized by wet chemistry, calcination, and electrodeposition. The synergistic effect of CuO nanowires and NiCoMn-LDH nanosheets has a significant enhancement effect on electrode materials. At the same time, the Mn content plays a decisive role in regulating and optimizing the morphology and electrochemical performance of electrode materials. The optimized CuO@NiCoMn-LDH, a binder-free electrode, exhibits excellent electrochemical performance. It displays a high specific capacity of 2.66 mA h cm−2 (20.7 F cm−2, 336.71 mA h g−1) at 10 mA cm−2 and satisfactory cycling stability (under a current density of 30 mA cm−2, after 3000 cycles, the capacity retention rate is 94.82%). In addition, an asymmetric supercapacitor (ASC) is built using the CuO@NiCoMn-LDH electrode as the positive electrode and Fe3O4@C/CuO electrode as the negative electrode to demonstrate its practical applicability in energy storage devices. At a power density of 4.79 mW cm−2, the ASC device can achieve a maximum energy density of 2.67 mW h cm−2. Two ASC devices are used as the power source of the light emitting diode (LED), which can emit light continuously for 15 minutes, showing great potential in energy storage device applications. [ABSTRACT FROM AUTHOR]

Single-phase magnesium molybdate, MgMoO4, is successfully synthesized by a facile sol-gel method. Attributed to the multielectron reaction and the synergistic effect of the elements molybdenum (Mo) and magnesium (Mg), the MgMoO4 electrode exhibits excellent electrochemical properties. After activation, benefiting from the decrease in particle size and the uniform nanosphere morphology, the MgMoO4 electrodes can deliver a stable high specific capacity of about 1060 mA h g−1 at a current density of 100 mA g−1 after 600 cycles. Based on the important role of the activation process, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and scan rate cyclic voltammetry (CV) measurement methods were employed to reveal the effect of the activation process on the electrochemical behavior of the electrode material. Furthermore, by combining the in situ X-ray diffraction (XRD) and ex situ X-ray photoelectron spectroscopy (XPS) results, we illustrate the lithium storage mechanism of the MgMoO4 electrode in detail. [ABSTRACT FROM AUTHOR]

Uniform lithium deposition is a benefit to achieving high-energy-density lithium metal batteries. There are many effective methods to suppress the dendritic growth of metallic lithium and promote the application of the lithium anode. However, the designation of lithiophilic sites at the atomic level remains a huge challenge. Herein, a two-dimensional porous conjugated porphyrin polymer linked by two acetylenic linkages from an in situ coupling reaction has been prepared on copper foil and employed as the lithiophilic host. The four electron-rich pyrrolic nitrogen atoms in the porphyrin building block and the linkage electron-rich sp-hybridized carbon atoms were regarded as precise lithiophilic sites, resulting in a decreased nucleation overpotential and dendrite free morphology. With uniform lithium deposition, the electrochemical performance of the electrode was significantly improved in regard to the overpotential, coulombic efficiency and lifespan. This work expands the precise construction of lithiophilic sites at the atomic level and benefits to further development of high-energy density lithium metal batteries. [ABSTRACT FROM AUTHOR]

A new material design strategy is developed to prepare high-performance flexible electrochemical electrodes. Carbon nanotubes (CNTs) and nickel/nickelous hydroxide (Ni/Ni(OH)2) are compounded through a chemical plating method and hydrothermal process. A single-side printing method is used to combine the active material and a flexible cotton substrate. The interfinger microstructure of the textile electrode can greatly facilitate charge/ion transfer at the electrode–electrolyte interface. One side of the fabric, which is untreated, could directly contact with human skin, providing a comfortable and user-friendly surface. With the CNTs/Ni/Ni(OH)2 ternary composite as a positive electrode and CNTs as a negative electrode, we assembled an in-plane asymmetrical micro-supercapacitor device (SF-NPCs). Thanks to a synergistic effect, SF-NPCs displays a high energy density of 0.29 W h cm−2 at a power density of 7.2 W cm−2. The operating window is extended to 1.5 V, and the device displays good potential for applications in the field of smart textiles. [ABSTRACT FROM AUTHOR]

Amorphization is considered to be an effective way to enhance the electrochemical performances of electrode materials due to the existence of isotropy and numerous defects. Herein, an amorphous hierarchically structured MnO2/acetylene black (a-MnO2/AB) composite is successfully fabricated via a redox method and subsequent mechanical ball milling. The a-MnO2/AB composite is composed of approximately 300 nm flower-like amorphous MnO2 submicron spheres and acetylene black particles with a diameter of about 50 nm. The a-MnO2/AB electrode exhibits an initial coulombic efficiency of 73.2%, excellent rate capabilities of 318 mA h g−1 at 9.6 A g−1, and high specific capacity retention of 1300 mA h g−1 after 300 cycles at 1 A g−1. The amorphous structure can provide more channels for rapid lithium-ion transmission due to the disorder and defects, and the ion-diffusion coefficient (∼5 × 10−7 cm2 s−1) is higher than those of crystalline materials. Due to the strong interactions (Mn–O–C bonds) between MnO2 and AB as a result of the ball milling, the composite shows low charge transport resistance and small volume changes during the discharging/charging process. This work provides a facile route for the construction of amorphous hierarchically structured Mn-based oxides as anodes for lithium-ion batteries (LIBs). [ABSTRACT FROM AUTHOR]

The single-phase binary nickel vanadate Ni2V2O7 was successfully synthesized by a simple solid-state method to explore novel anode materials for lithium-ion batteries. After an activation process, the Ni2V2O7 electrode exhibited excellent electrochemical performance with a stable, high specific capacity of about 960 mA h g−1 at a current density of 100 mA g−1, which is attributed to the multiple valence states and the synergistic effect of the transition elements V and Ni. Even at a high current density of 2000 mA g−1, a stable specific capacity of about 400 mA h g−1 was still obtained. Considering the influence of the activation process on the electrochemical performance of the Ni2V2O7 electrode, we studied the origin of the excellent electrochemical performance, where the improved lithium diffusion coefficient and increased pseudocapacitive contribution caused by the activation process led to a significant improvement in the electrochemical performance, including rate capacity and cycle stability. By combining in situ X-ray diffraction (XRD) and ex situ X-ray photoelectron spectroscopy (XPS) methods, for the first time, we illustrate the detailed lithium storage mechanism of the Ni2V2O7 electrode during the lithium insertion/extraction process. [ABSTRACT FROM AUTHOR]

Lithium–sulfur batteries have a high theoretical energy density but they need better sulfur host materials to retain the lithium polysulfide shuttle effect, which results in the batteries' capacity fading. Titanium carbide MXene (Ti3C2Tx MXene) is an excellent host for the sulfur cathode because of its layered-stacked structure and many surface termination groups. The sulfur content in S/Ti3C2Tx MXene composites is an important factor affecting the cathodes' electrochemical performance. In this work, S/Ti3C2Tx MXene composites with different sulfur contents are prepared by a one-step hydrothermal process, and the influence of the sulfur content in the S/Ti3C2Tx MXene composite on the S/Ti3C2Tx MXene cathode's electrochemical performance is studied. When the mass ratio of sulfur to MXene in the reactant is 4 : 1, the sulfur nanoparticles are uniformly filled in the layered-stacked structure. The layered-stacked structure can buffer the volume expansion of sulfur during cycling and the surface termination groups exhibit strong adsorption of LiPSn. Thus, the S/MXene composite with an optimum sulfur content (67.0 wt%) demonstrates an excellent electrochemical performance, including a high initial reversible capacity (1277 mA h g−1 at 0.5 C) and the best cycling performance (1059 mA h g−1 at 0.5 C after 100 cycles). This work offers a guide to developing advanced S-based cathode materials with an appropriate S content for lithium sulfur batteries. [ABSTRACT FROM AUTHOR]

The use of a carbon thermal reduction roasting method to recover lithium resources from spent lithium-ion batteries (S-LIBs) provides an important opportunity for recycling S-LIBs. The preferential extraction of Li via reduction roasting has been widely studied; however, the extraction of Li from mixed cathode materials has been rarely reported. Herein, we propose a method based on carbon thermal reduction to preferentially extract Li from mixed cathode materials. It was confirmed that there are differences in carbon thermal reduction products at 700 °C–850 °C by the thermodynamic analysis of the carbon thermal reduction process. At the same time, the effects of factors such as roasting temperature, roasting time, and material ratio on Li leaching efficiency were investigated. The Li recovery rate reached 98.86% under the optimal conditions of holding at 750 °C for 4 h with a molar ratio of mixed cathode materials to graphite of 1 : 0.25. Recovered Li2CO3 can be directly used as a lithium source for the regeneration of cathode materials. This study will provide new opportunities for the efficient recycling of spent lithium-ion batteries (S-LIB) mixtures. [ABSTRACT FROM AUTHOR]

Atomically precise silver nanoclusters (Ag-NCs) are known as a hot research area owing to their brilliant features and they have attracted an immense amount of research attention over the last year. There is a lack of sufficient understanding about the Ag-NC synthesis mechanisms that result in optimal silver nanoclusters with an appropriate size, shape, and morphology. In addition, the coexisting flexible coordination of silver ions, the argentophilic interactions, and coordination bonds result in a high level of sophistication in the self-assembly process. Furthermore, the expansion of clusters by the organic ligand to form a high dimensional structure could be very interesting and useful for novel applications in particular. In this study, a novel two-dimensional 14-nucleus silver poly-cluster was designed and synthesized by the combination of two synthetic methods. The high nucleus silver cluster units are connected together via tetradecafluoroazelaic acid (CF2) and this leads to the high stability of the polymer. This highly stable conductive poly-cluster, with bridging groups of difluoromethylene, displays a high energy density (372 F g−1 at 4.5 A g−1), excellent cycling stability, and great capacity. This nanocluster shows a high power density and long cycle life over 6000 cycles (95%) and can also tolerate a wide range of scan rates (5 mV s−1 to 1 V s−1), meaning it could act as a green energy source. [ABSTRACT FROM AUTHOR]

An Ni–Zn battery is a distinguished member in the family of closed Zn-based batteries due to its ideal power density and voltage. However, when it is employed as a power supply for electric vehicles, its defects in terms of specific capacitance and energy density become obvious. Herein, to resolve this problem, a hybrid battery system was created through a combination of Ni–Zn and Zn–air batteries at the cell level. In a hybrid battery system, oxygen vacancy rich NiO with S,N co-modified mesoporous carbon as a matrix was used as the cathode material. This cathode material showed a high specific capacitance of 202.1 mA h g−1 at 1.0 A g−1. When the current density reduces to 20 A g−1, this value decreases to 130.2 mA h g−1, which implies that 64.4% of specific capacitance was retained. It also exhibits excellent OER and ORR activities. For the hybrid battery system, when the discharge process was carried out at 1 mA cm−2, there were two voltage plateaus at 1.72 and 1.12 V, which originated from Ni–Zn and Zn–air, respectively. In this case, its specific capacitance and energy density reaches 800.3 mA h g−1 and 961 W h kg−1, respectively. The hybrid battery also possesses perfect stability during multi-cycle charge–discharge tests. The construction of this hybrid battery system develops a new road to prepare a power supply device with high performance. [ABSTRACT FROM AUTHOR]

Although binary metal oxides with high theoretical specific capacities and power densities are widely investigated as promising anode materials for lithium-ion batteries (LIBs), their poor cycling stability and huge volume expansion largely limit their extensive application in practical electrode materials. Herein, we report a facile strategy to synthesize hollow NiCo2O4 nanowires through direct calcination of binary metal–organic frameworks (MOFs) in air. When evaluated as an anode material for LIBs, NiCo2O4 nanowires deliver a reversible capacity of 1310 mA h g−1 at a current density of 100 mA g−1 after 100 cycles. Even at a high current density of 1 A g−1, NiCo2O4 nanowires exhibit long-term cycling stability with a capacity of 720 mA h g−1 after 1000 cycles. The outstanding lithium-storage performance can be attributed to the unique structures with 1D porous channels, which are beneficial for the fast transfer of Li+ ions and electrolyte and alleviate the strain caused by the volume expansion during cycling processes. [ABSTRACT FROM AUTHOR]

Structure and defect manipulation are regarded as efficacious strategies to boost the electrochemical activity of electrode materials. Herein, the construction of one-dimensional (1D) porous S-doped Co3O4 nanorods with rich oxygen vacancies is demonstrated through a facile metal–organic framework-engaged strategy. Starting from a Co-NTA (NTA = nitrilotriacetic acid) precursor, the S-doped Co3O4 nanorods were obtained after calcination and sulfurization. As a faradaic electrode material, the S-doped Co3O4 nanorods exhibited enhanced specific capacitance (319.3 C g−1 at 0.5 A g−1) in comparison with the Co3O4 intermediate product (98.3 C g−1) and the Co-NTA precursor (40.2 C g−1). Besides, it showed an ultra-high rate capability of 83.3% with a 20-fold increase in current density (10 A g−1). The hybrid supercapacitor comprising the S-doped Co3O4 (cathode) and the activated carbon (anode) showed a high energy density of 38.1 W h kg−1 at a power density of 800 W kg−1, and 31.1 W h kg−1 was maintained at 8000 W kg−1. It also has excellent electrochemical stability, and 87.57% of its initial capacitance was maintained after 5000 cycles, demonstrating great prospects in electrochemical energy storage applications. The excellent energy storage property of the S-doped Co3O4 is due to its unique 1D S-doped Co3O4 porous nanorod structure, i.e., large surface area, easy diffusion of ions, good conductivity, and rich redox reactions. This work may pave the way for the fabrication of desirable electrode materials through vacancy defects and nano-/microstructure engineering. [ABSTRACT FROM AUTHOR]

Layered Li-rich/Mn-rich NMC (LMR-NMC) is characterized by high initial specific capacities of more than 250 mA h g−1, lower cost due to a lower Co content and higher thermal stability than LiCoO2. However, its commercialisation is currently still hampered by significant voltage fade, which is caused by irreversible transition metal ion migration to emptied Li positions via tetrahedral interstices upon electrochemical cycling. This structural change is strongly correlated with anionic redox chemistry of the oxygen sublattice and has a detrimental effect on electrochemical performance. In a fully charged state, up to 4.8 V vs. Li/Li+, Mn4+ is prone to migrate to the Li layer. The replacement of Mn4+ for an isovalent cation such as Sn4+ which does not tend to adopt tetrahedral coordination and shows a higher metal–oxygen bond strength is considered to be a viable strategy to stabilize the layered structure upon extended electrochemical cycling, hereby decreasing voltage fade. The influence of Sn4+ on the voltage fade in partially charged LMR-NMC is not yet reported in the literature, and therefore, we have investigated the structure and the corresponding electrochemical properties of LMR-NMC with different Sn concentrations. We determined the substitution limit of Sn4+ in Li1.2Ni0.13Co0.13Mn0.54−xSnxO2 by powder X-ray diffraction and transmission electron microscopy to be x ≈ 0.045. The limited solubility of Sn is subsequently confirmed by density functional theory calculations. Voltage fade for x = 0 and x = 0.027 has been comparatively assessed within the 3.00 V–4.55 V (vs. Li/Li+) potential window, from which it is concluded that replacing Mn4+ by Sn4+ cannot be considered as a viable strategy to inhibit voltage fade within this window, at least with the given restricted doping level. [ABSTRACT FROM AUTHOR]

An oxacalix[4]arene-Ce(III) complex viz. L–Ce(III) has been introduced for the selective detection of As(V) and Cr(VI) oxyanions in aqueous medium. The binding mode of L–Ce(III) + AsO43−/CrO42− was completely investigated with fluorometric titration, time resolve fluorescent decay and FTIR analyses. Photoinduced electron transfer (PET) and chelation-enhanced fluorescence (CHEF) play an important role in the sensing of these oxyanions. The characteristic fluorescence of the L–Ce(III) complex has been quenched by AsO43− and CrO42− through cascading the ligating sites. Cyclic voltammetry (CV) experiments with various scan rates suggest that the electrochemical processes on the electrodes were controlled by diffusion. Both the analytes exhibit a lower limit of detection (LOD) below their standard EPA permissible limits. Moreover, the probe successfully detects the oxyanions in environmental real samples with excellent recovery ranging from 97 to 101%. [ABSTRACT FROM AUTHOR]

Microwave-driven hydrometallurgical (MW-HM) method has been adopted to extract spinel-type Li4Ti5O12 (LTO) and orthorhombic-type LiFePO4 (LFP) from naturally occurring Ilmenite (FeTiO3) within 2 h unlike the conventional process that requires >30 h. We have successfully demonstrated aliovalent-Nb5+ doping and carbon coating with N, Br co-doping upon the pyrolysis of a polypyrrole-(PPy)-Br2 charge-transfer-(CT)-complex via MW-hydrothermal and MW-solid state heating within 30 min. Further, we also investigated the effect of carbon coating and co-doping of LTO and LFP electrodes at high C-rate performance of the lithium battery. XRD, XPS, FTIR, and Raman spectroscopy results confirmed the co-existence of dual-phase Li4Ti5O12/rutile-TiO2 (LTO-RTO) with substitution-induced transition of Ti4+ → Ti3+ in spinel-LTO due to Nb5+ and N, Br co-doping, which facilitates fast Li+ ion and electron transfer at the electrode–electrolyte interface. Conversely, in situ Nb5+ doped LiFePO4 combined with ex situ carbon-coating with N, Br co-doping improved the overall electronic conductive behavior. The UV-Visible absorption spectra and Tauc plots further support the decrease in the band gap upon co-doping, thus promoting n-type electronic behavior of the electrodes. A significant enhancement in the discharge-capacities of the carbon-coated N, Br co-doped Li4Ti4.97 Nb0.03O12/rutile-TiO2 (NBC-LTNO-RTO) and pristine anode in the range of 174–148 mA h g−1 and 167–125 mA h g−1 was exhibited at different rates in the range of 0.2 C–20 C with 97% and 94% capacity retention, respectively. Instead, the carbon-coated N, Br co-doped LiFe0.99 Nb0.01PO4 (NBC-LFNP) and pristine cathode exhibited discharge capacities in the range of 169–73 mA h g−1 and 136–65 mA h g−1 at different rates in the range of 0.2 C–20 C with 92% and 40% capacity retention for 500 cycles, respectively. Hence, this innovative, rapid, and sustainable chemical process for the fabrication of the modified cathode and anode from the earth abundant ilmenite ore as the single source with high-rate capability and ultra-stability can be used for high-power and safer lithium-ion energy storage. [ABSTRACT FROM AUTHOR]

Through the integration of Zn-Co3O4 and Zn-air batteries at the cell level, a hybrid battery was assembled, which possessed a higher voltage and power density than a common Zn-air battery. In this hybrid battery, the cathode material is composed of oxygen-vacancy-rich Co3O4−x and N, S-co-doped carbon derived from a metal–organic framework; a Zn plate acts as the anode. With a current of 1 A g−1, the specific capacity of the cathode material achieves 144 mA h g−1. A four-electron process dominates the oxygen reduction reaction of the cathode material with a half wave potential of 0.78 V. In the oxygen evolution reaction, the η10 potential of the cathode material is merely 365 mV. When discharged at 1 mA cm−2, the hybrid Zn battery shows two discharge plateaus at 1.75 V and 1.11 V. Its specific capacity and energy density reach 711 mA h g−1 and 810 W h kg−1, respectively. This battery also inherits superior power density from the Zn-Co3O4 battery. Its peak power density occurs at 43.6 mW cm−2, and this value is obviously higher than that of the Zn-air battery built from the same cathode material. The hybrid battery also exhibits excellent stability with a capacity and charge–discharge voltage that are well maintained after long time periods. This study integrates two distinct batteries into one power source to develop a hybrid Zn battery, which possesses high voltage, specific capacity and superior power and energy densities. [ABSTRACT FROM AUTHOR]

MnV2O6 is a promising anode material for lithium ion batteries with high theoretical specific capacity, abundant reserves and inexpensive constituent elements. However, in the process of lithization and de-lithization, the MnV2O6 anode material will form an amorphous phase, leading to collapse of its original layered structure; this greatly decreases its lithium storage capacity and specific capacity and affects its long-term cycle performance. In this study, 2D accordion-like MnV2O6 nanosheets with Co-doping are obtained via a hydrothermal route. The cobalt ions partially replace the positions of the manganese ions, and the emergence of Co3+ ions is inferred to induce the formation of a built-in electric field in the electrode to enhance the electrochemical behaviour of MnV2O6, presenting a high capacity of 1005.9 mA h g−1 after hundreds of cycles. The capacitive contribution to the total capacity is investigated to obtain insight into the kinetic analysis of its electrochemical behaviour. This study sheds light on an effective strategy to obtain excellent electrochemical behavior of MnV2O6-based materials and other transition metal oxides as electrodes for lithium storage. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) few-layer MXene nanosheets have attracted extensive attention due to their great potential for high-rate energy storage devices, but a simplified method to synthesize these structures with good cycling and rate performances is still a challenge for the MXene family. In this work, a one-step method to synthesize 2D few-layer niobium carbide (Nb2CTx) MXene nanosheets by etching Nb2AlC powder is reported for the first time. A sample of the few-layer Nb2CTx electrode shows a high specific capacity of 354 mA h g−1 at 0.05 A g−1 with a long cycling lifetime. The specific capacity can be stabilized at 225 mA h g−1 after 800 cycles at 1.0 A g−1. The one-step synthesis of unassisted few-layer Nb2CTx MXene nanosheets paves the way for the exploration of Nb2CTx-based composite materials and applications. [ABSTRACT FROM AUTHOR]

A rational design of heterostructures for electrode materials is highly desired for boosting the electrochemical performance, but it is still challenging, especially through a cost-effective method. Herein, novel NiCo2O4 nanosheet-decorated leaf-like Co3O4 nanoarrays have been constructed on a Ni foam using a leaf-like Co-based metal–organic framework (Co-MOF-L) template, which can be simply prepared in an aqueous solution at room temperature. Combining the merits of MOF derivatives and the free-standing core–shell heterostructure, the leaf-like Co3O4@NiCo2O4 nanoarray electrode displayed a high specific capacity of 544.2 C g−1 at 1 A g−1, which is almost 9.3 times that of Co3O4 (58.3 C g−1) and 6 times that of NiCo2O4 (92.1 C g−1). It also displayed a good rate capacity (65.5% at 10 A g−1) and superior long-term stability (93.0% capacity retention over 5000 cycles at 10 A g−1). Moreover, a hybrid supercapacitor (HSC) assembled from the battery-type Co3O4@NiCo2O4 electrode and a capacitive activated carbon (AC) electrode delivered a high energy density of 36 W h kg−1 at a high power density of 852 W kg−1 with good cycling stability, demonstrating a capacity retention of 89.5% after 10 000 cycles at 10 A g−1. Furthermore, two connected HSCs could light up a red light-emitting diode (LED). Therefore, the as-fabricated leaf-like Co3O4@NiCo2O4 nanoarrays hold great promise as binder-free electrodes in electrochemical energy storage devices. [ABSTRACT FROM AUTHOR]

SiC&Si@CNT composite 3D frameworks were successfully synthesized via an in situ reduction method of a C@SiO2@CNT precursor. Owing to the extremely large amount of heat derived from magnesiothermic reduction, SiC particles of the SiC&Si@CNT composite were obtained by a reaction between Si and C. The amount of SiC could be adjusted by changing the poly-dopamine coating time. The SiC&Si@CNT composite is composed of reduced nano Si, fine SiC and CNTs. The as-prepared materials, particularly the SiC&Si@CNT-1 sample, show superior cycling performance and electrochemical characteristics as anode materials for lithium-ion batteries. In particular, the specific capacity of the SiC&Si@CNT-1 electrode reaches 1051.44 mA h g−1 at 1 A g−1 even after 880 cycles. Furthermore, the SiC&Si@CNT-1 electrode delivered ideal reversible capacities of 671.58 mA h g−1 and 476.71 mA h g−1 at high current densities of 4 A g−1 and 8 A g−1, respectively. The porous nanostructure of the SiC&Si@CNT composite 3D framework is beneficial for shortening the path of lithium-ion diffusion inside the electrode, alleviating the volume expansion and contraction during the cycling process. These results suggest that the SiC&Si@CNT composite 3D frameworks can be used as appropriate anode materials for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Prussian blue analogues (PBAs) are a family of classic coordination polymers. They have been widely applied in various fields including electrochemical sensors. Cubic nanoparticle structure is their common morphology. It is still a great challenge to design a hollow and two-dimensional (2D) PBA material. Of course, it will be a significant surprise if a hollow cube and 2D sheet can be integrated into one material. In this work, we designed a simple one-step synthetic strategy and resolved the above difficulty, wherein a hollow cubic PBA covered by 2D ultrathin nanosheets was successfully constructed, namely hollow tremella-like PBA (HTPBA). Furthermore, Ni foam (NF) as a substrate was introduced to obtain a self-supporting HTPBA/NF-12 electrode. HTPBA/NF-12, as a bifunctional electrochemical sensor electrode, exhibited distinguished catalytic performance towards glucose and nitrite, including remarkable selectivity, reproducibility, sensitivity for glucose (21 410 μA mM−1 cm−2) and nitrite (1248 μA mM−1 cm−2), wide linear range of 2–1250 μM and 5–3380 μM, along with low detection limit of 0.056 μM and 0.38 μM, respectively. More importantly, HTPBA/NF-12 electrodes possessed good reusability and practicability even in goat serum. In this study, we developed a simple and effective strategy to fabricate 2D@3D PBA material with excellent electrocatalytic activity and provide a totally new viewpoint in the PBA sensing field. [ABSTRACT FROM AUTHOR]

The aim of this study was to unveil the mechanisms of SiO2/ZrO2 (SSZ) anode materials through electrochemical analysis and to understand the effect of various Si/Zr molar ratios (Si/Zr = 0.5, 1, and 2) on the performance of SSZ anode materials with these mechanisms. The 2-SSZ (Si/Zr = 2) electrode had a much higher capacity than that of the 0.5- or 1-SSZ (Si/Zr = 0.5 or 1) electrode. It exhibited superior cycling performance when compared to commercial graphite (theoretical capacity of 372 mA h g−1). The 2-SSZ had a capacity of 461 mA h g−1 at a high current density of 100 mA g−1 over 30 cycles. These characteristics are due to the effects from each of the different reversible materials formed by the SSZs. Zr2Si and Zr5Si3, ZrSi, or ZrSi2 were formed by the 0.5-, 1-, and 2-SSZs, respectively, which would affect the reversible storage capacity. ZrSi2 provided an increase in the possible reaction area for the guest species (lithium ions) at the empty interstitial site in the host materials as well as a large area for accommodating a volume change. It was supportive by maintaining the lattice constant and reducing the ratio of the structure distortion. Furthermore, the 2-SSZ structure consisted of an overall amorphous structure with a crystalline structure related to the Zr–O–Si bond unlike the 0.5- and 1-SSZs which had an overall crystalline structure. Such a combined structure of 2-SSZ was advantageous for providing good capacity due to the amorphous structure and an efficient pathway for electron transport and little pulverization due to the crystalline structure. This structure led to its superior performance and long lifespan. [ABSTRACT FROM AUTHOR]

Drycast methods have been used frequently in recent decades to adsorb a range of synthetic catalysts on electrodes. The uncoordinated multilayers that are formed via this immobilization method can however have a strong impact on the electrocatalytic reaction pathway as slow electron transfer and intermolecular interactions can alter the chemistry of the catalysts on the surface. To gain insight into the structure of Fe porphyrin Hangman catalysts during electrocatalytic oxygen reduction a combination of electrochemistry and surface enhanced resonance Raman spectroscopy (SERRS) was applied. The Hangman complexes were attached to the electrodes via different methods and the influence of the immobilisation technique on oxygen chemistry was studied. In multilayer systems, new intermediates could be identified via potential dependent SERRS that were not present in solution or in monolayer systems under catalytic conditions. A comparison of Raman spectra obtained either via Soret or Q-band excitation showed that the porphyrin symmetry is strongly distorted under reducing conditions, which was interpreted by the transient formation of dimer complexes during catalysis. [ABSTRACT FROM AUTHOR]

To meet the increasing requirements of lithium-ion batteries (LIBs) as energy sources for mobile electronic devices and electric vehicles, great efforts are being made to develop cathode and anode materials with high specific capacity and lifetime stability. Herein, we report a Li-rich one-dimensional (1D) Li1.13Mn0.26Ni0.61O2 (0.3Li2MnO3·0.7LiNiO2, LMO@LNO) cathode and a nitrogen-doped carbon-decorated NiO (NC@NiO) anode material prepared from 1D Ni(OH)2 nanowires (NWs) for application in full LIBs. The as-prepared 1D Li-rich LMO@LNO cathode displays a high discharge capacity (184.4 mA h g−1), high coulombic efficiency (73.9%), long-term cyclability, and good rate performance in comparison with pristine LiNiO2 (LNO). Moreover, the 1D NC@NiO composite anode exhibits a high discharge capacity (914.5 mA h g−1), high coulombic efficiency (76.8%), long cycling life, and better rate performance, as compared with bare NiO. A full LIB consisting of the nanostructured Li-rich LMO@LNO cathode and the NC@NiO anode delivers a high capacity of over 167.9 mA h g−1 between 4.0 and 0.1 V. These enhanced electrochemical characteristics suggest that the full LIB configuration with 1D Li-rich LMO@LNO and NC@NiO composites holds promise as a next-generation secondary battery platform. [ABSTRACT FROM AUTHOR]

LiNi0.6Co0.2Mn0.2O2 cathode material has been surface-modified by coating with ultrathin TiO2via atomic layer deposition (ALD) technology to improve the electrochemical performance of LiNi0.6Co0.2Mn0.2O2 cathodes for lithium ion batteries. Within the cut-off voltage of 2.5–4.3 V, the coated sample delivers an initial discharge capacity of 187.7 mA h g−1 at 0.1 C and with a capacity retention about 85.9% after 100 cycles at 1 C, which provides a significant improvement in terms of discharge capacity and cyclability, as compared with those of the bare one. Such enhanced electrochemical performance of the coated sample is ascribed to its high-quality ultrathin coating of amorphous TiO2, which can protect the active material from HF attack, withstand the dissolution of metal ions in the electrode and favor the lithium diffusion of oxide as proved by electrochemical impedance spectroscopy (EIS) tests. TiO2 coating via the ALD process provides a potential approach for battery factories to surface-modify Ni-rich electrode materials so as to realize improvements in electrochemical performance. [ABSTRACT FROM AUTHOR]

NiS2 hollow spheres are successfully prepared by a one-step template free method. Meanwhile, α-NiS hollow spheres can also be synthesized via the calcination of the pre-obtained NiS2 hollow spheres at 400 °C for 1 h in air. The electrochemical performances of the as-prepared NiS2 and α-NiS hollow sphere products are evaluated. When used for supercapacitors, compared with NiS2 hollow spheres, the α-NiS hollow sphere electrode shows a large specific capacitance of 717.3 F g−1 at 0.6 A g−1 and a good cycle life. Furthermore, NiS2 and α-NiS hollow spheres are successfully applied to fabricate non-enzymatic glucose sensors. In particular, the α-NiS hollow spheres exhibit good catalytic activity for the oxidation of glucose, a fast amperometric response time of less than 5 s, and the detection limit is estimated to be 0.08 μM. More importantly, compared with other normally co-existing interfering species, such as ascorbic acid, uric acid and dopamine, the electrode modified with α-NiS hollow spheres shows good selectivity. Moreover, the α-NiS hollow spheres also present good capacity to remove Congo red organic pollutants from wastewater by their surface adsorption ability. [ABSTRACT FROM AUTHOR]

Nanocrystalline Li2MSiO4 (M = Fe, Mn) particles embedded between in situ formed rGO sheets are obtained by adopting customized solvothermal synthesis. An appreciable room temperature specific capacity of 149 mA h g-1 with 89% capacity retention and 210 mA h g-1 with 87% retention have been exhibited by Li2FeSiO4/rGO and Li2MnSiO4/rGO composites, corresponding to the participation of close to one and more than one lithium per formula unit respectively. The formation of nanocrystalline Li2MSiO4 (M = Fe, Mn) compounds in the desired phase and the complete wrapping of orthosilicates with rGO sheets are believed to be responsible for the excellent electrochemical behavior of the orthosilicate cathodes of the present study to best suit with requirements of rechargeable lithium-ion batteries. The abundant availability and eco-benignity advantages of Fe and Mn are valuable additions in the consideration of Li2MSiO4/rGO (M = Fe, Mn) cathodes as sustainable potential candidates. [ABSTRACT FROM AUTHOR]

Rational design and synthesis of efficient metal–organic frameworks (MOFs) as electrode modifiers for energy-related electrocatalytic applications are crucial for the development of clean-energy technologies. The present review focuses on recent work on robust earth-abundant heterogeneous catalysts based on pristine MOFs for the hydrogen evolution reaction (HER) and overall water splitting. These catalysts have been extensively studied as alternatives for noble metal-based ones, demonstrating "hydrogen economy" development prospects. In addition, novel strategies to enhance the conductivity, chemical stability and efficiency of MOF-based electrocatalysts are discussed. The best electrocatalysts even surpass the achievements of the platinum group of metals and MOF-derived catalysts in catalytic performance. The electrolytic cells with MOF-modified electrodes demonstrated excellent catalytic activity and can deliver a high current density at a voltage lower than that using the precious metal-based Pt/C cathodes and IrO2 anodes. In this review article, current approaches to design such MOF and MOF-modified electrode materials are summarized and analyzed. [ABSTRACT FROM AUTHOR]

The construction of multi-dimensional structured battery-type electrode materials is a promising strategy to develop high performance electrodes for supercapacitors. Herein, a series of battery-type Ni3S2@Co3S4 electrodes with different morphologies are synthesized by controlling the hydrothermal reaction time. Owing to the unique structure with independent but interconnected 2D nanosheets and 3D cubic frameworks, NCS-60 displays high conductivity, numerous active sites and good wettability behavior. It can deliver a high specific capacity of 388.9 mA h g−1 (3500 F g−1) at 1 A g−1, an outstanding rate capacity of maintaining 88.6% at 10 A g−1 and long cycle stability. The battery-type supercapacitor hybrid (BSH) device with active carbon (AC) as the negative electrode delivers an energy density of 41.8 W h kg−1 at the power density of 800 W kg−1. This study provides a feasible route for regulating the morphologies of in situ growth materials that improve the electrochemical performance of supercapacitors. [ABSTRACT FROM AUTHOR]