Highly porous NiCo2O4 Nanoflakes and nanobelts as anode materials for lithium-ion batteries with excellent rate capability

Morphology-Tunable Binary Transition Metal Oxide Heterostructure@Carbon Composites for Lithium-Ion Batteries

Heterostructures of binary and unary transition metal oxides (B and UTMOs) have demonstrated excellent electrochemical performance in lithium-ion batteries (LIBs) due to synergistic effects; however, there remains a lack of research combining multiple strategies for synergy enhancement. Herein, we present the development of crystallinity-controlled heterostructures based on nickel and cobalt oxides (NiCo2O4/NiO and NiO/Co3O4) with different morphologies (urchin- and flower-like structures, e.g., U-NiCo2O4/NiO and F-NiCo2O4/NiO) to investigate the influence of heterostructure combinations and morphologies on electrochemical performance in LIBs. The morphologies of the heterostructures were controlled by adjusting the fluoride concentration during the synthesis of the nickel-cobalt (Ni-Co) precursor, while heterostructure combinations were regulated by heat treatment under specific conditions. When used as anodes for LIBs, electrochemical analyses revealed that the carbon-coated urchin-like U-NiCo2O4/NiO (U-NiCo2O4/NiO@C) sample provided more efficient charge transfer and a shorter Li-ion transport pathway compared to its counterpart (F-NiCo2O4/NiO@C) due to its high surface area and distinctive morphological features. In addition, U-NiCo2O4/NiO@C exhibited superior electrochemical performance as an anode in LIBs than U-NiO/Co3O4@C, indicating that the advantageous effects of BTMO over UTMO can effectively enhance LIB performance. This facile synthesis approach provides a foundation for morphology-controlled heterostructures in the development of high-performance anode materials for LIB applications.

Active metals decorated NiCo2O4 yolk-shell nanospheres as nanoreactors for catalytic reduction of nitroarenes and azo dyes

Transition-metal oxides (TMOs) have received a great deal of research attention and have been widely used in a variety of fields. However, conventional TMOs do not possess high specific surface area, sufficient active site on their surfaces, and limited their applications in catalysis. This study presents a two-step method for synthesizing active metal (M) decorated NiCo2O4 (M/NiCo2O4, M = Pd or Cu) nanospheres with yolk-shell nanostructures. Taking advantage of the unique morphology and the combination of dual active components (i.e., active NiCo2O4 substrate and decorated active metal), the as-prepared M/NiCo2O4 yolk-shell nanospheres can be employed as nanoreactors in the organic reactions. In catalyzing the reduction of a representative nitroarene (i.e., 4-NP) by NaBH4, the Pd/NiCo2O4 nanoreactors exhibit a superior catalytic efficiency to their counterparts (Cu/NiCo2O4 and NiCo2O4). The turnover frequency is much higher than that of various TMOs supported nanocatalysts have been reported over the past five years. Furthermore, the Pd/NiCo2O4 nanoreactors show excellent stability and common applicability of the reduction of various substituted nitrobenzenes and azo dyes. This work provides new rational design concept and preparation strategy for efficient nanoreactors with dual active components and sheds light on the practical application of chemical reactions.

Metal-organic-framework derived Zn-V-based oxide with charge storage mechanism as high-performance anode material to enhance lithium and sodium storage

Transition metal oxides have been extensively studied due to their large theoretical capacities, but their practical application has been hampered by low electrical conductivity and dramatic volume fluctuation during cycling. In this work, we synthesized Zn3V2O8 material using Zn-V-MOF (metal-organic framework) as a sacrificial template to improve the electrochemical characteristics of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Unique dodecahedral structure, larger specific surface area and higher ability to mitigate volume changes, improve the electrochemical reaction active site while accelerating ion transport. Zn3V2O8 with 2-methylimidazole as a ligand demonstrated a discharge capacity of 1225.9 mAh/g in LIBs and 761.6 mAh/g in SIBs after 300 cycles at 0.2 C. Density functional theory (DFT) calculation illustrates the smaller diffusion barrier energy and higher specific capacity in LIBs that is ascribed to the fact that Li has a smaller size and hence its diffusion is easier. This study may lead to a path for the manufacturing of high-performance LIBs and SIBs.

Surficial grafting of organoimido moieties enhances the capacity performance of oxometallic clusters

Molybdenum trioxide (MoO₃) with a theoretical specific capacity of 1117 mA h g^-1 is widely considered a promising anode material for lithium-ion batteries. However, the irreversible conversion reactions, low electrical conductivity, and detrimental volume expansion upon Li intercalation between the one-dimensional layered structures of MoO₃ hinder its practical implementation. Herein, we report a facile synthetic protocol that allows surficial modification by replacing the terminal and bridging oxo groups of molybdenum oxide clusters. Successful organoimido functionalization resulted in a large cathodic shift in Mo(VI/V) reduction by 0.6 V, pronounced electronic communication between the organic moiety and the metal-oxide unit, and significant increase in electrical conductivity (80-100 Ω interfacial charge-transfer resistance). Combined with the enlarged active surface area due to the structural hindrance induced by the organic functionality, the steady specific capacity of the organoimido-modified molybdenum oxide clusters was greater than 1200 mA h g^-1 at 900 mA g^-1 at the end of 360 cycles, where the best value of 1653 mA h g^-1 was achieved for the nitroaniline-substituted species. The steady capacity of 480 mA h g^-1 was achieved in the fast charge-discharge process (3000 mA g^-1) over 1400 cycles. The results indicate that the surficial modification of metal oxides with organo moieties using our facile synthetic method has broad application potential for metal oxides to be used as high-capacity electrode materials in the future.

Nanostructured Molybdenum-Oxide Anodes for Lithium-Ion Batteries: An Outstanding Increase in Capacity

This work aimed at synthesizing MoO₃ and MoO₂ by a facile and cost-effective method using extract of orange peel as a biological chelating and reducing agent for ammonium molybdate. Calcination of the precursor in air at 450 °C yielded the stochiometric MoO₃ phase, while calcination in vacuum produced the reduced form MoO₂ as evidenced by X-ray powder diffraction, Raman scattering spectroscopy, and X-ray photoelectron spectroscopy results. Scanning and transmission electron microscopy images showed different morphologies and sizes of MoO_x particles. MoO₃ formed platelet particles that were larger than those observed for MoO₂. MoO₃ showed stable thermal behavior until approximately 800 °C, whereas MoO₂ showed weight gain at approximately 400 °C due to the fact of re-oxidation and oxygen uptake and, hence, conversion to stoichiometric MoO₃. Electrochemically, traditional performance was observed for MoO₃, which exhibited a high initial capacity with steady and continuous capacity fading upon cycling. On the contrary, MoO₂ showed completely different electrochemical behavior with less initial capacity but an outstanding increase in capacity upon cycling, which reached 1600 mAh g^-1 after 800 cycles. This outstanding electrochemical performance of MoO₂ may be attributed to its higher surface area and better electrical conductivity as observed in surface area and impedance investigations.

Realizing the enhanced cyclability of a cactus-like NiCo2O4 nanocrystal anode fabricated by molecular layer deposition

Lithium-ion batteries with conversion-type anode electrodes have attracted increasing interest in providing higher energy storage density than those with commercial intercalation-type electrodes. However, conversion-type materials exhibit severe structural instability and capacity fade during cycling. In this work, a molecular layer deposition (MLD)-derived conductive Al₂O₃/carbon layer was employed to stabilize the structure of the cactus-like NiCo₂O₄ nanocrystal (NC) anode. The conductive Al₂O₃/carbon network and cactus-like NiCo₂O₄ NCs are beneficial for fast Li⁺/e^- transport. Moreover, the Al₂O₃/carbon buffer-layer can prevent the NiCo₂O₄ NCs from agglomeration and form a steady solid electrolyte interphase (SEI), thus hampering the penetration of the electrolyte. Owing to these advantages, the assembled NiCo₂O₄@Al₂O₃/carbon half battery shows a high reversible capacity (931.2 mA h g^-1 at 2 A g^-1) and long-term stability of 290 mA h g^-1 at 5 A g^-1 over 500 cycles. Quantitative analyses further reveal the fast kinetics and the capacitance-battery dual model mechanism in the 3D core-shell structures. The design and introduction of MLD-derived hybrid coating may open a new way to conversion-type and alloy-type anode materials beyond NiCo₂O₄ to achieve high cyclability.

Low-cost 3D porous sea-hedgehog-like NiCo2O4/C as anode for Li-ion battery

Carbon is effective additive to improve cyclic performances of transition metal oxides for lithium ion battery, while common graphene or carbon nanotube is expensive. In this study, waste of rice husk is used to prepare low cost carbon. A composite of NiCo₂O₄/carbon is synthesized via hydrothermal method plus calcination. At hydrothermal time of 6 h, the material displays 3-D sea hedgehog-like structure with radial corn cob-shaped nanorod. The NiCo₂O₄/carbon presents better rate performances, coulombic efficiency and cyclic stability than pristine NiCo₂O₄, showing stable capacity of 1018 mAhg^-1 (52.6% higher than NiCo₂O₄) after 100 cycles at 0.1 Ag^-1. For long-term cycling during 500 cycles at 0.5 Ag^-1, the composite anode exhibits a reversible capacity of ∼880 mAhg^-1, with high retention of 92.2%. The capacity is still retained ∼715 mAhg^-1 even after 1000 cycles at 1 Ag^-1.

NiCo2O4 Nano-/Microstructures as High-Performance Biosensors: A Review

Non-enzymatic biosensors based on mixed transition metal oxides are deemed as the most promising devices due to their high sensitivity, selectivity, wide concentration range, low detection limits, and excellent recyclability. Spinel NiCo2O4 mixed oxides have drawn considerable attention recently due to their outstanding advantages including large specific surface area, high permeability, short electron, and ion diffusion pathways. Because of the rapid development of non-enzyme biosensors, the current state of methods for synthesis of pure and composite/hybrid NiCo2O4 materials and their subsequent electrochemical biosensing applications are systematically and comprehensively reviewed herein. Comparative analysis reveals better electrochemical sensing of bioanalytes by one-dimensional and two-dimensional NiCo2O4 nano-/microstructures than other morphologies. Better biosensing efficiency of NiCo2O4 as compared to corresponding individual metal oxides, viz. NiO and Co3O4, is attributed to the close intrinsic-state redox couples of Ni3+/Ni2+ (0.58 V/0.49 V) and Co3+/Co2+ (0.53 V/0.51 V). Biosensing performance of NiCo2O4 is also significantly improved by making the composites of NiCo2O4 with conducting carbonaceous materials like graphene, reduced graphene oxide, carbon nanotubes (single and multi-walled), carbon nanofibers; conducting polymers like polypyrrole (PPy), polyaniline (PANI); metal oxides NiO, Co3O4, SnO2, MnO2; and metals like Au, Pd, etc. Various factors affecting the morphologies and biosensing parameters of the nano-/micro-structured NiCo2O4 are also highlighted. Finally, some drawbacks and future perspectives related to this promising field are outlined.

Dual-functional NiCo2S4 polyhedral architecture with superior electrochemical performance for supercapacitors and lithium-ion batteries

Dual-functional NiCo₂S₄ polyhedral architectures with outstanding electrochemical performance for supercapacitors and lithium-ion batteries (LIBs) have been rationally designed and successfully synthesized by a hydrothermal method. The as-synthesized NiCo₂S₄ electrode for supercapacitor exhibits an outstanding specific capacitance of 1298Fg^-1 at 1Ag^-1 and an excellent rate capability of ~80.4% at 20Ag^-1. Besides, capacitance retention of 90.44% is realized after 8000 cycles. In addition, the NiCo₂S₄ as anode in LIBs delivers high initial charge/discharge capacities of 807.6 and 972.8mAhg^-1 at 0.5C as well as good rate capability. In view of these points, this work provides a feasible pathway for assembling electrodes and devices with excellent electrochemical properties in the next generation energy storage applications.

Optimisation of the internal structure of ceramic membranes for electricity production in urine-fed microbial fuel cells

The need to find a feasible alternative to commercial membranes for microbial fuel cells (MFCs) poses an important challenge for the practical implementation of this technology. This work aims to analyse the influence of the internal structure of low-cost terracotta clay-based membranes on the behaviour of MFCs. To this purpose, 9 different combinations of temperature and time were used to prepare 27 MFC separators. The results show that the temperature has a significant effect on both porosity and pore size distribution, whereas the ramp time do not show a significant influence on these parameters. It was observed that kilning temperatures higher than 1030 °C dramatically reduce the porosity of the samples, reaching a minimum value of 16.85%, whereas the pore size increases as the temperature also increases. Among the membranes with similar porosities, those with a medium pore size distribution exhibited the lowest bulk resistance allowing MFCs to reach the highest power output (94.67 μW cm^-2). These results demonstrate the importance of not only the porosity but also the pore size distribution of the separator in terms of MFC performance and longevity, which for these experiments was for 90 days.

Hierarchically self-assembled NiCo2O4 nanopins as a high-performance supercapacitor cathodic material: a morphology controlled study

In this study, 3D hierarchically self-assembled NiCo₂O₄ nanopins were synthesized by a morphology controlled hydrothermal method. Structure, morphology, and composition of the samples were investigated using FT-IR, XRD, EDS, and SEM methods. Electrochemical tests such as cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) studies were done in a three-electrode system with 1.0 M Na₂SO₄ solution as the electrolyte for the supercapacitive study of the samples on a carbon paste electrode for the first time. The results confirmed the high-performance supercapacitive behavior of the dense nanostructure and acceptable stability during the charge–discharge cycle. The specific capacitance for the dense self-organized nanopins was calculated using a galvanostatic charge/discharge experiment which gave 2168 F g⁻¹ at a current density of 5 A g⁻¹.

In this study, 3D hierarchically self-assembled NiCo₂O₄ nanopins were synthesized by a morphology controlled hydrothermal method.

Electrospinning-based construction of porous Mn3O4/CNFs as anodes for high-performance lithium-ion batteries

Porous one-dimensional Mn₃O₄/CNFs composites are fabricated and used as anode materials for Li-ion batteries; they exhibit excellent electrochemical performance.

High-performance spinel NiMn2O4 microspheres self-assembled with nanosheets by microwave-assisted synthesis for supercapacitors

Spinel NiMn₂O₄ microspheres self-assembled with nanosheets directly grown on a 3D nickel foam were successfully prepared by a facile microwave-assisted hydrothermal process.

Formation of uniform porous yolk-shell MnCo2O4 microrugby balls with enhanced electrochemical performance for lithium storage and the oxygen evolution reaction

Mixed transition metal oxides with favorable electrochemical properties are promising electrode materials in energy storage and conversion systems. In this work, uniform porous yolk-shell MnCo₂O₄ (denoted as YSM-MCO) microrugby balls have been synthesized by simple annealing treatment of metal carbonates with a microrugby ball shape in air. Benefiting from the desired porous structure and composition, the as-synthesized YSM-MCO exhibits enhanced electrochemical performance when investigated as anode materials for lithium-ion batteries and electrocatalysts for the oxygen evolution reaction. The YSM-MCO demonstrates remarkable lithium storage properties with a good cycling stability (94% capacity retention over 200 cycles at 0.5 A g^-1) and superior rate capability (414 mA h g^-1 at 5 A g^-1). In addition, the YSM-MCO also exhibits better OER activity than most of the reported MnCo₂O₄-based electrocatalysts.

Lithiated NiCo2O4 Nanorods Anchored on 3D Nickel Foam Enable Homogeneous Li Plating/Stripping for High-Power Dendrite-Free Lithium Metal Anode

Lithium (Li) metal is one of the promising anode materials in the next-generation high-energy batteries, but Li dendrite growth and a big volume change during cycling result in low Coulombic efficiency (CE), short lifespan, and safety hazards, thereby impeding practical implementation of Li in rechargeable batteries. Herein, we report a highly stable and dendrite-free Li metal anode based on a three-dimensional (3D) conductive and lithiophilic scaffold comprising lithiated NiCo₂O₄ nanorods grown on nickel foam (LNCO/Ni). The nanorods grown on 3D Ni foam with a large surface area effectively reduce the averaged electrical current in the electrode, and the conformal Li₂O coating produced in situ on the lithiated NiCo₂O₄ nanorods provides the surface lithiophilicity enabling stable Li plating/stripping without Li dendrite growth even at a high current density of 5 mA cm^-2. The LNCO/Ni-Li anode shows a low voltage hysteresis of 16 mV, high CE of 98.7%, and stable cycling without obvious voltage fluctuation for over 500 cycles (1000 h) at a current density of 1 mA cm^-2. Specifically, for a scalable Li loading of 20 mA h cm^-2 on LNCO/Ni, no growth of Li dendrite and electrode thickness fluctuations are observed. The full cell consisting of the LNCO/Ni-Li anode and the LiFePO₄ cathode exhibits a high rate capability and CE as high as 99.6% for more than 160 cycles. Our study reveals a new strategy to develop stable Li-metal anodes for high-energy batteries.

Synthesis of Sea Urchin-Like NiCo2O4 via Charge-Driven Self-Assembly Strategy for High-Performance Lithium-Ion Batteries

In this study, hydrothermal synthesis of sea urchin-like NiCo₂O₄ was successfully demonstrated by a versatile charge-driven self-assembly strategy using positively charged poly(diallydimethylammonium chloride) (PDDA) molecules. Physical characterizations implied that sea urchin-like microspheres of ~ 2.5 μm in size were formed by self-assembly of numerous nanoneedles with a typical dimension of ~ 100 nm in diameter. Electrochemical performance study confirmed that sea urchin-like NiCo₂O₄ exhibited high reversible capacity of 663 mAh g^-1 after 100 cycles at current density of 100 mA g^-1. Rate capability indicated that average capacities of 1085, 1048, 926, 642, 261, and 86 mAh g^-1 could be achieved at 100, 200, 500, 1000, 2000, and 3000 mA g^-1, respectively. The excellent electrochemical performances were ascribed to the unique micro/nanostructure of sea urchin-like NiCo₂O₄, tailored by positively charged PDDA molecules. The proposed strategy has great potentials in the development of binary transition metal oxides with micro/nanostructures for electrochemical energy storage applications.

A hollow-nanosphere-based microfluidic biosensor for biomonitoring of cardiac troponin I

Cardiovascular diseases (CVDs) are the leading causes of death worldwide.

Black Phosphorus Stabilizing Na2Ti3O7/C Each Other with an Improved Electrochemical Property for Sodium-Ion Storage

Sodium-ion batteries have increasingly been considered as an attractive alternative to lithium-ion batteries for large-scale applications. High specific capacity and suitable working potential anode materials are one of the keys to search for future developments. Here, a novel and stable sodium titanate/carbon-black phosphorus (NTO/C-BP) hybrids are first fabricated as a promising anode material for advanced sodium-ion batteries. Under the protection of argon (Ar) atmosphere, the direct high-energy mechanical milling of the BP nanoparticle and NTO/C results in the formation of NTO/C-BP hybrids. In other words, the BP nanoparticle can be interconnected with bare NTO by P-O-Ti bonds and/or form stable P-C bonds with the carbon coating layer on the surface of NTO. The NTO/C-BP hybrids are not only beneficial for enhancing specific capacity but also have a great protective effect on the exposure of BP to air by the synergistic effect between BP and NTO/C. The results show that the NTO/C-BP hybrids can deliver very high specific capacity (∼225 mA h g^-1 after 55 cycles at 20 mA g^-1, ∼183 mA h g^-1 after 100 cycles at 100 mA g^-1). It is expected from these scientific findings that forming stable P-C bonds and P-O-Ti bonds in this work can serve as a guidance to other Ti-based and P-based electrode materials for practical large-scale application of sodium-ion batteries.

Three-dimensional porous self-assembled chestnut-like nickel-cobalt oxide structure as an electrochemical sensor for sensitive detection of hydrazine in water samples

Three-dimensional NiCo₂O₄ is a kind of superior sensing material owing to its high electron transfer capability, large available surface area and numbers of active sites. In this work, NiCo₂O₄ of the three-dimensional chestnut-like structure were easily achieved through a one step hydrothermal process. Afterwards, the morphology and structure were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Based on the three-dimensional porous chestnut-like NiCo₂O₄, an electrochemical sensor for hydrazine (N₂H₄) detection is fabricated. This electrochemical platform can realize good selectivity, excellent stability, high sensitivity (∼2154.4 μA mM^-1 cm^-2), and low detection limit (0.3 μM), as well as a wide linear range from 1 μM to 1096 μM. The synergistic effect of nickel-cobalt in such mixed transition metal oxides which Co in Co₃O₄ is partially replaced by Ni are beneficial for enhancing sensing properties. This study proves that three-dimensional porous chestnut-like NiCo₂O₄ is electrochemically active for catalytic performance which is particular and promising material for good application in the practical detection of N₂H₄.

Electrodeposited binder-free NiCo2O4@carbon nanofiber as a high performance anode for lithium ion batteries

Binder-free nickel cobaltite on a carbon nanofiber (NiCo₂O₄@CNF) anode for lithium ion batteries was prepared via a two-step procedure of electrospinning and electrodeposition. The CNF was obtained by annealing electrospun poly-acrylonitrile (PAN) in nitrogen (N₂). The NiCo₂O₄ nanostructures were then grown on the CNF by electrodeposition, followed by annealing in air. Experimental results showed that vertically aligned NiCo₂O₄ nanosheets had uniformly grown on the surface of the CNF, forming an interconnected network. The NiCo₂O₄@CNF possessed considerable lithium storage capacity and cycling stability. It exhibited a high reversible capacity of 778 mAhg^-1 after 300 cycles at a current density of 0.25 C (1 C = 890 mAg^-1) with an average capacity loss rate of 0.05% per cycle. The NiCo₂O₄@CNF had considerable rate capacities, delivering a capacity of 350 mAhg^-1 at a current density of 2.0 C. The outstanding electrochemical performance can be mainly attributed to the following: (1) The nanoscale structure of NiCo₂O₄ could not only shorten the diffusion path of lithium ions and electrons but also increase the specific surface area, providing more active sites for electrochemical reactions. (2) The CNF with considerable mechanical strength and electrical conductivity could function as an anchor for the NiCo₂O₄ nanostructure and ensure an efficient electron transfer. (3) The porous structure resulted in a high specific surface area and an effective buffer for the volume changes during the repeated charge-discharge processes. Compared with a conventional hydrothermal method, electrodeposition could significantly simplify the preparation of NiCo₂O₄, with a shorter preparation period and lower energy consumption. This work provides an alternative strategy to obtain a high performance anode for lithium ion batteries.

Hierarchical porous NiCo2O4 nanosheet arrays directly grown on carbon cloth with superior lithium storage performance

Binary metal oxides have been explored as advanced candidates in lithium-ion battery (LIB) anodes due to their high specific capacity. Herein, the hierarchical structures of porous NiCo₂O₄ nanosheets directly grown on a conductive carbon cloth substrate (3D NCO-PSA/CC) were obtained by a facile in situ synthetic strategy. When applied as a binder-free LIB anode, it exhibited satisfactory performance with a high discharge capacity (a first discharge capacity of 2090.8 mA h g^-1 and a stable capacity of 1687.6 mA h g^-1 at 500 mA g^-1), superior rate capacity (discharge capacity of 375.5 mA h g^-1 at 6000 mA g^-1) and excellent reversibility (coulombic efficiency of approximately 100%). The outstanding performances should be attributed to the 3D porous structures, nanosheets and good conductivity of NCO-PSA/CC that could not only ensure the rapid transport of Li⁺ ions and electrons but also remit the huge volume change during lithiation/delithiation processes. Undoubtedly, the present facile and effective strategy can be extended to other binary metal-oxide materials for use as high-performance energy storage and conversion devices.

High electrochemical performance of 3D highly porous Zn0.2Ni0.8Co2O4 microspheres as an electrode material for electrochemical energy storage

3D highly porous Zn_0.2Ni_0.8Co₂O₄ microspheres unveil superior electrochemical energy storage properties.

Facile preparation of monodisperse NiCo2O4 porous microcubes as a high capacity anode material for lithium ion batteries

Monodisperse NiCo₂O₄ porous microcubes were used as anode materials for lithium-ion batteries, and they exhibit outstanding rate capability and cycling stability.

N doped carbon coated V2O5 nanobelt arrays growing on carbon cloth toward enhanced performance cathodes for lithium ion batteries

Highly flexible, binder-free cathodes for lithium ion batteries were fabricated by utilizing N doped carbon to coat V₂O₅ (V₂O₅@N-C) nanobelt arrays growing on carbon cloth. Such a robust architecture endows the electrode with effective ion diffusion and charge transport, resulting in high rate capability (135 mA h g⁻¹ at 10C) and excellent cycling performance (215 mA h g⁻¹ after 50 cycles at 0.5C).

Highly flexible, binder-free cathodes for lithium ion batteries were fabricated by utilizing N doped carbon to coat V₂O₅ (V₂O₅@N-C) nanobelt arrays growing on carbon cloth.

Top-down fabrication of hierarchical nanocubes on nanosheets composite for high-rate lithium storage

A top-down method was developed to synthesize a “nanocubes on nanosheets” hierarchical structure composite for high-rate lithium storage.

Enhanced Electrocatalytic Activity of Pt/3D Hierarchical Bimodal Macroporous Carbon Nanospheres

Proton exchange membrane fuel cells require electrocatalysts with a high platinum (Pt) loading, large active surface area, and favorable hydrodynamic profile for practical applications. Here, we report the design of three-dimensional hierarchical bimodal macroporous carbon nanospheres with an interconnected pore system, which are applied as an electrocatalyst support. Carbon-supported Pt (Pt/C) catalysts were prepared by aerosol spray pyrolysis followed by microwave chemical deposition. The hierarchical porous structures not only increased the dispersion of Pt nanoparticles but also improved catalytic performance. A hierarchical bimodal macroporous Pt/C catalyst with a mixture of 30 and 120 nm size pores showed the best performance. The electrochemical surface area and mass activity values of this support were 96 m² g^-1-Pt and 378 mA mg^-1-Pt, respectively at a Pt loading of 15 wt %.

Hierarchical NiCo2O4 Micro- and Nanostructures with Tunable Morphologies as Anode Materials for Lithium- and Sodium-Ion Batteries

NiCo₂O₄ microrods with open structures are successfully synthesized using a solvothermal method. Compared with those of dense microspheres, the one-dimensional (1D) porous microrods show much higher capacities and stability for both Li- and Na-ion batteries due to the 1D open structure facilitating fast ion transport and buffering volumetric change during charge/discharge. This work demonstrates that the electrochemical performance of NiCo₂O₄ is highly dependent on morphologies of the active material.

Core-shell ZnCo2O4@TiO2 nanowall arrays as anodes for lithium ion batteries

In this paper ZnCo₂O₄ nanowall arrays (NWAs) were first obtained through self-assembly followed by calcination. Then atomic layer deposition was used to fabricate core-shell ZnCo₂O₄@TiO₂ NWAs as anode materials for lithium ion batteries (LIBs). The hierarchical NWA nanostructure has fast ion diffusion and electron transport at the electrode/electrolyte interface, while the excellent chemical stability of the TiO₂ shell can protect the ZnCo₂O₄ NWAs from volume expansion during the charge and discharge processes. The core-shell ZnCo₂O₄@TiO₂ core-shell NWAs composite is versatile as an anode material and exhibits enhanced electrochemical performance for LIBs. The initial capacity was 1598 mA h g^-1 (Coulombic efficiency reached 84.0%), and the reversible capacity after 90 cycles was 827 mA h g^-1 at a current density of 100 mA g^-1, showing high capacity and good cycling stability (much better than ZnCo₂O₄ NWAs). The ZnCo₂O₄@TiO₂ nanocomposite also showed excellent rate capability with a reversible capacity of 532 mA h g^-1 even at a current rate of 4500 mA g^-1. The encouraging experimental results suggest that the novel core-shell structure NWAs have great potential for practical applications in LIBs.

Self-assembly of porous CuO nanospheres decorated on reduced graphene oxide with enhanced lithium storage performance

A Li full cell assembled by porous CuO-NSs/RGO anode and commercial LiFPO₄ cathode can light up an LED lamp.