Excellent Long-term Performance Research Articles

Cu-coated Li3V2(PO4)3/carbon as high-performance cathode material for lithium-ion batteries

The development of lithium-ion batteries is hindered by the lack of appropriate low-cost cathode materials with high performance. Here, the preparation of Cu-coated Li3V2(PO4)3/C (x% Cu-LVPC) composites is reported via a chemical precipitation and self-reduction method. With an optimized Cu coating content of 2.0 wt%, the 2.0% Cu-LVPC composite displays the best electrochemical properties. The initial discharge capacity of 2.0% Cu-LVPC is 175 mA h g−1 at 0.15 C (30 mA g−1) in the voltage range from 3.0 to 4.8 V and the capacity retention is 86.3% after 50 cycles, whereas pristine LVPC has an initial capacity of 163 mA h g−1 and retains 82.2% of the capacity after 50 cycles. Moreover, the rate capacity of 2.0% Cu-LVPC is also increased under different current densities and 2.0% Cu-LVPC exhibits excellent long-term cycling performance of 89 mA h g−1 after 1000 cycles at 10 C. The enhanced electrochemical properties are attributed to the uniform coating of the metal conductor Cu on the LVPC surface, which is conducive to electron transfer and extraction/insertion of Li+ ions.

3D printing coaxial fiber electrodes towards boosting ultralong cycle life of fibrous supercapacitors

Fiber-shaped asymmetric supercapacitors (FASCs) with high electrochemical performance have become an important component of modern wearable fiber-shaped electronic devices. However, terrible cycling stability restricts their further development in energy storage fields. The most common strategy is to coat the carbon layer on the surface of the electrode materials, whereas the carbon layer is prone to peel off during bending process, which decrease the cyclic stability of the electrodes or devices. To overcome this challenge, the coaxial fiber electrodes have been achieved via 3D printing direct ink writing (DIW) technology and the FASC device has the excellent electrochemical cycle performance owing to the compact architectures of the positive and negative electrode. Benefited from the suitable charge match of two electrodes and the uniformity of carbon layer coated on the surface of electrodes, the as-fabricated FASC device embraces high areal capacitance of 318.82 mF cm-2, superior areal energy density of 143.15 μWh cm-2, and excellent long-term cycling performance with capacitance retention of 98.63% after 12,000 cycles.

A tailored multi-functional catalyst for ultra-efficient styrene production under a cyclic redox scheme

Styrene is an important commodity chemical that is highly energy and CO2 intensive to produce. We report a redox oxidative dehydrogenation (redox-ODH) strategy to efficiently produce styrene. Facilitated by a multifunctional (Ca/Mn)1−xO@KFeO2 core-shell redox catalyst which acts as (i) a heterogeneous catalyst, (ii) an oxygen separation agent, and (iii) a selective hydrogen combustion material, redox-ODH auto-thermally converts ethylbenzene to styrene with up to 97% single-pass conversion and >94% selectivity. This represents a 72% yield increase compared to commercial dehydrogenation on a relative basis, leading to 82% energy savings and 79% CO2 emission reduction. The redox catalyst is composed of a catalytically active KFeO2 shell and a (Ca/Mn)1−xO core for reversible lattice oxygen storage and donation. The lattice oxygen donation from (Ca/Mn)1−xO sacrificially stabilizes Fe3+ in the shell to maintain high catalytic activity and coke resistance. From a practical standpoint, the redox catalyst exhibits excellent long-term performance under industrially compatible conditions.

Construction of Explicit Symplectic Integrators in General Relativity. I. Schwarzschild Black Holes

Abstract Symplectic integrators that preserve the geometric structure of Hamiltonian flows and do not exhibit secular growth in energy errors are suitable for the long-term integration of N-body Hamiltonian systems in the solar system. However, the construction of explicit symplectic integrators is frequently difficult in general relativity because all variables are inseparable. Moreover, even if two analytically integrable splitting parts exist in a relativistic Hamiltonian, all analytical solutions are not explicit functions of proper time. Naturally, implicit symplectic integrators, such as the midpoint rule, are applicable to this case. In general, these integrators are numerically more expensive to solve than same-order explicit symplectic algorithms. To address this issue, we split the Hamiltonian of Schwarzschild spacetime geometry into four integrable parts with analytical solutions as explicit functions of proper time. In this manner, second- and fourth-order explicit symplectic integrators can be easily made available. The new algorithms are also useful for modeling the chaotic motion of charged particles around a black hole with an external magnetic field. They demonstrate excellent long-term performance in maintaining bounded Hamiltonian errors and saving computational cost when appropriate proper time steps are adopted.

Bulk Modification of Thermoplastic Polyurethanes for Self-Sterilization of Trachea Intubation.

Implantable medical devices are widely used, but biomaterial-associated infections (BAIs) impose a huge economic burden and increase the mortality of patients. Therefore, BAIs are a serious concern that must be urgently resolved. Materials with antibacterial properties have become hotspots of current research and development. In the present work, quaternized chitosan (QCS) is used as an antibacterial agent and blended with thermoplastic polyurethane (TPU) to create an antibacterial material for tracheal intubation tubes. The modified TPU material (QCS-TPU) exhibited good mechanical properties and excellent long-term antibacterial performance. Under in vitro hydrodynamic conditions, QCS-TPU retained its strong antibacterial properties. QCS-TPU also possessed a low hemolysis rate and cytotoxicity. The current work is expected to provide a facile and feasible strategy for the preparation of antibacterial catheters and aid in the discovery of promising clinical applications to prevent BAIs.

Bulk and surface degradation in layered Ni-rich cathode for Li ions batteries: Defect proliferation via chain reaction mechanism

Ni-rich cathode materials have emerged as a class of low-cost and high-energy-density Li ions batteries cathodes. However, the bulk and surface degradation of Ni-rich cathode remains controversial. By transmission electron microscopy (TEM), the bulk and surface degradation of nickel-rich cathode are distinguished by the causes and development time. Structure deterioration with rock-salt phase is observed in the bulk and surface region. The triggered phase transition by defect chain reaction (DCR) mechanism is unveiled by the first-principle-calculation simulations. The critical factor in DCR mechanism is the migration barrier of Ni. The decrease in migration barrier of Ni due to the oxygen vacancy and the lowering of the system energy by the Li ion compensation causes extra cation mixing and lattice distortion. Hence, Ni ion migration introduces strain perpendicular to the Ni layers with oxygen defects and Li vacancies, which leads to dislocations and defects with lattice distortion. Based on the model, a manganese oxide coating method was proposed to adjust the valence state of nickel and avoid the oxygen defects. The treated cathode presented an excellent long-term cycling performance, about 80.6% of the initial capacity after 200 cycles.

Experimental investigation on the long-term behaviour of prefabricated timber-concrete composite beams with steel plate connections

This paper presents the results of long-term experiments performed on three timber-concrete composite (TCC) beams. An innovative fabricated steel plate connection system, which consists of screws and steel plates embedded in concrete slabs, was adopted in the TCC beam specimens. The adopted shear connection can provide dry-type connection for TCC beams. Steel plates were embedded in concrete slabs while the concrete slab was constructed in factories. The timber beam and concrete slab can be assembled together using screws at the construction site. In this experimental programme, the beam specimens were subjected to constant loading for 613 days in indoor uncontrolled environments. The influence of long-term loading levels and the number of shear connections on the long-term performance of TCC beams was investigated and discussed. The mid-span deflection, timber strain, and interface relative slip at the positions of both connections and beam-ends were recorded throughout the long-term tests. It was found the long-term deflection of the TCC beam increased by approximately 60% while the long-term loads were doubled. Under the influence of the variable temperature and humidity, the TCC specimens with 8 shear connections showed slighter fluctuations compared with the TCC beam with 6 shear connections. In the 613-day observation period, the maximum deflection increment recorded was 6.56 mm for the specimen with eight shear connections and 20% loading level. A rheological model consisting of two Kelvin bodies was employed to fit the curves of creep coefficients. The final deflections predicted of all specimens at the end of 50-year service life were 2.1~2.7 times the initial deflections caused by the applied loads. All beam specimens showed relative small increments in mid-span deflection, strain and relative slip over time without any degradations, demonstrating the excellent long-term performance of TCC beams using the innovative steel plate connection system, which is also easily fabricated.

Exploration of antifouling zwitterionic polyimide ultrafiltration membrane based on novel aromatic diamine monomer

In this study, a new kind of aromatic diamine monomer named as 1,4-bis(4-aminophenyl)piperazine (BANPZ) was particularly designed and synthesized, and then the novel zwitterionic polyimide (ZPI) was prepared through a two-step process including polycondensation and quaternary amination reaction. The chemical structures of the prepared monomer and polymers were identified by FTIR and 1H NMR measurements, respectively. Meanwhile, the inherent viscosities, molecular weights, solubility behaviors and thermal properties of two obtained polymers were thoroughly characterized. Compared with the control polyimide (PI) membrane, the presence of zwitterionic groups considerably improve the hydrophilicity of the ZPI membrane, thereby enhancing the water permeability to some extent without obviously affecting the rejection ratio. Based on the static protein adsorption and dynamic cycle ultrafiltration experiments, the ZPI membrane exhibited persistent antifouling property, which was demonstrated by the flux decline ratio and filtration resistance. In particular, the water flux recovery ratio of the ZPI membrane was retained at 96.0% after a three-cycles of BSA solution filtration, which was much higher than that of the PI membrane (76.7%), suggesting excellent long-term performance stability. This new approach provided a valuable strategy of combining polymer chemical structure optimization and mature non-solvent induced phase separation (NIPS) method, which could greatly drive the development and application range of separation membranes.

The influence of pulse magnetic field intensity on the morphology and electrochemical properties of NiCoS alloys

In this study, we synthesized arrayed NiCoS alloys as electrode material of supercapacitors via a customized hydrothermal reaction device assisted by pulse magnetic field and studied the effect of pulse magnetic field intensity on the morphology and electrochemical performances of NiCoS alloys. The results showed that the diameter of the rod-shaped NiCoS alloys reaches its minimum value of 10 nm and the arrangement of the arrayed grains is most regular at a peak current density of 9Adm−2 flowing through the electromagnetic induction coil. Consequently, the specific capacity of that sample reaches a maximum value of 161.2 mAhg−1 at 2Ag−1, which drops to 118.7 mAhg−1when the current density increases from 2Ag−1 to 10 Ag−1. The optimized sample also exhibits an excellent long-term cycling performance with a retention ratio of 84.6% over 5000 cycles in 2 M KOH electrolyte. The remarkable electrochemical performances may be attributed to the effect of pulse magnetic field on the nucleation and growth of NiCoS alloys, which could enlarge its surface area and improve its crystal dendrite quality.

Performance Enhancement of Polymer Electrode Materials for Lithium-Ion Batteries: From a Rigid Homopolymer to Soft Copolymers.

Synthesizing redox-active units containing polymers is a promising route for improving the cycling stability of organic electrode materials. However, constructing uniform electrode architectures with good polymer dispersion is a big challenge in the case of polymer electrode materials. In this work, we design and synthesize two anthraquinone-containing copolymers and compare their electrochemical performance with that of the corresponding homopolymer. It is uncovered that the copolymers with soft units in the main chain display increased chain flexibility, thus leading to a slightly increased solubility. Because of this, the soft copolymers are less likely to precipitate during solvent volatilization of electrode preparation and thus can form more uniform electrode architectures. The cyclic voltammogram and electrochemical impedance spectroscopy measurements indicate that copolymer electrodes display decreased polarization and improved kinetics compared with the homopolymer electrode. The copolymers exhibit significantly enhanced cycling stability and improved rate performance. After 100 cycles, both copolymers reveal very high capacity retention of above 98%, while the homopolymer retains only 71% of its highest capacity. Moreover, the copolymer can discharge/charge at 1C for over 2000 cycles with almost no capacity fading, indicating excellent long-term cycling performance. This work further demonstrates the importance of molecular structure and electrode architecture in determining the electrochemical performance of polymer electrode materials.

Water-Pillared Sodium Vanadium Bronze Nanowires for Enhanced Rechargeable Magnesium Ion Storage.

Owing to the advantages of high safety, low cost, high theoretical volumetric capacities, and environmental friendliness, magnesium-ion batteries (MIBs) have more feasibility for large-scale energy storage compared to lithium-ion batteries. However, lack of suitable cathode materials due to sluggish kinetics of magnesium ion is one of the biggest challenges. Herein, water-pillared sodium vanadium bronze nanowires (Na2 V6 O16 ·1.63H2 O) are reported as cathode material for MIBs, which display high performance in magnesium storage. The hydrated sodium ions provide excellent structural stability. The charge shielding effect of lattice water enables fast Mg2+ diffusion. It exhibits high specific capacity of 175 mAh g-1 , long cycle life (450 cycles), and high coulombic efficiency (≈100%). At high current density of 200 mA g-1 , the capacity retention is up to 71% even after 450 cycles (compared to the highest capacity), demonstrating excellent long-term cycling performance. The nature of charge storage kinetics is explored. Furthermore, a highly reversible structure change during the electrochemical process is proved by comprehensive electrochemical analysis. The remarkable electrochemical performance makes Na2 V6 O16 ·1.63H2 O a promising cathode material for low-cost and safe MIBs.

Synthesis and characterization of novel zwitterionic poly(aryl ether oxadiazole) ultrafiltration membrane with good antifouling and antibacterial properties

Notably, zwitterionic polymers have attracted increasing attention to various potential applications in membrane-based separation processes on account of the good biocompatibility, superior antifouling and excellent antimicrobial property. In this contribution, a novel membrane material based on zwitterionic poly(aryl ether oxadiazole) (Z-PAEO) was designed and synthesized by a facile and convenient two-step route consist of polycondensation and quaternary amination reaction. Z-PAEO ultrafiltration membrane was subsequently fabricated by the scalable non-solvent induced phase separation (NIPS) method. The chemical structures and compositions of these prepared polymers were determined by using 1H NMR, FTIR and XPS measurements, and their inherent viscosities, molecular weights, thermal properties and solubility behaviors were extensively characterized, respectively. The presence of zwitterionic groups considerably improved the porosity, pore size and hydrophilicity of Z-PAEO membrane, which was helpful to the permeability of the obtained membrane without obviously affecting the protein rejection. Interestingly and significantly, the as-prepared Z-PAEO membrane displayed superior and persistent antifouling performance as well as antibacterial property. The water flux recovery ratio of Z-PAEO membrane (97.6%) after a three-cycles of BSA solution filtration was much higher than that of the reference PAEO membrane (78.4%), suggesting excellent long-term performance stability. It can be expected that developing novel zwitterionic polymers can significantly expand the application scopes of separation membrane.

Implementation of high-performance electrochromic device based on all-solution-fabricated Prussian blue and tungsten trioxide thin film

Electrochromic devices (ECDs) rely on interfacial charge-transfer and ion transport. They generally suffer from a decline in their operational performance, which is caused by irreversible redox reactions, ion accumulation, or overpotential at the solution/electrode interface. Herein, we implement high-performance ECDs with excellent optical modulation (45.9%), fast switching speed (3 s), high coloring efficiency (98.1 cm2/C), and excellent long-term performance (>1000 cycles) under the bias of 0.7 V through in-depth optimization of device components and modulation of its driving characteristics. Three requirements for device structure and operation were considered to implement high-performance ECDs; i) uniformity and robustness of the electrochromic (EC) film in the working electrode (WE), ii) high surface area and fast redox properties of the complementary electrode, iii) total offsetting of the charge applied in the device during the coloring/bleaching process. Various electrodeposition methods such as galvanostatic, potentiostatic, pulsed potential, and triple pulse potential application were exploited to fabricate the active layers, and the active layers produced under optimized conditions through individual studies on the most stable film stability, electrochemical behavior, EC and ion storage characteristics were assembled in the devices. Under all optimized conditions, we constructed high-performance ECDs composed of electrodeposited Prussian blue (PB) as an EC layer and tungsten trioxide (WO3) as a complementary layer, respectively. In particular, the offset of the charge applied to the device between the coloring and bleaching processes drastically improved the long-term stability of EC performance under low operating bias. The results provide a useful basis for enhancing the performance of ECDs and can be widely applied to various ECDs.

Transparent Thin-Film Silicon Solar Cells for Indoor Light Harvesting with Conversion Efficiencies of 36% without Photodegradation.

With the development of the Internet of Things (IoT), indoor photovoltaics are attracting considerable interest owing to their potential to benefit various IoT-related fields. Therefore, this study investigates the use of transparent hydrogenated amorphous silicon (a-Si:H) solar cells for a broad range of applications, including indoor light harvesting. High-gap triple layers were employed in the a-Si:H solar cells to obtain a high shunt resistance and high short-circuit current, JSC, and open-circuit voltage, VOC, under indoor illumination. Additionally, multiple color-adjusting layers were added without noticeable costs to the conversion efficiency. The maximum efficiency of 36.0% was obtained at a transmittance of 20.44% under white LED light (3000 lx and 0.92 mW cm-2). Furthermore, the fabricated transparent solar cells show excellent long-term performance, sustaining over 99% of original efficiency under continuous indoor light illumination for 200 h. These cells could accelerate the progress of energy harvesting in IoT applications and facilitate the construction of integrated photovoltaics.

Fabrication of Ni–B/TiC–Y2O3 nanocomposites by one-step electrodeposition at different duty cycle and evaluation of structural, surface and performance as protective coating

A novel Ni–B/TiC–Y2O3 nanocomposites has been synthesized by one-step pulse electrodeposition at different duty cycle as protective coating. The effects of pulse duty cycle on its structural, surface, corrosion an wear behavior were evaluated. The coating exhibits compact and hill-valley like structure. The average roughness (Sa) was about 56–161 nm and duty cycle of 30% benefits low roughness and fine-grained structure. The crystallite size is 16–19 nm and slightly varied with process parameters. The coating exhibits the preferred orientation of Ni (111) texture. AFM and XPS were utilized to analyze the surface properties. Electrochemical impedance and wear studies illustrated that duty cycle of 30% was the optimal parameter for the best corrosion and wear resistance, exhibiting an excellent long-term performance stability in 3.5 wt% NaCl corrosive solution. This coating exhibits good potentiality for various industrial applications in aggressive medium.

Polyvinylamine/amorphous metakaolin mixed-matrix composite membranes with facilitated transport carriers for highly efficient CO2/N2 separation

In order to obtain high-performance facilitated transport membrane for CO2/N2 separation, we prepared mixed-matrix composite membranes (MMCMs) by polyvinylamine (PVAm) and the amorphous layered metakaolin (MK), with polysulfone (PSf) as a support. The attenuated total reflectance Fourier-transform infrared spectroscopy results revealed the strong interfacial interaction between the PVAm and the oxygen-rich MK. MK was homogenously dispersed in the PVAm matrix, as confirmed by scanning electron microscopy. The MMCMs showed the enhanced CO2 separation performance with a CO2 permeance of 152 GPU and a CO2/N2 selectivity of 78 at 1 bar under pure gas condition, when the MK loading was 1 wt%. These values were much higher than those of the PVAm membrane loaded with the crystalline multi-layer kaolin, with a CO2 permeance of 85 GPU and a CO2/N2 selectivity of 55. The enhanced separation performance is mainly ascribed to the increase of the intermolecular distance between the polymer chains after the addition of the MK sheets to the PVAm matrix, which was validated by X-ray diffraction. Moreover, the addition of the amorphous MK to PVAm can increase more tortuosity of gas transport than multi-layered and other shape fillers in the MMCMs as a result of the homogenous dispersion of the fully exfoliated MK in the membrane. Besides, the MMCMs exhibited excellent long-term stability performance even under mixed-gas conditions for over 300 h, with a CO2 permeance of 188 GPU and a CO2/N2 selectivity of 83.8, surpassing the Robeson's upper bound proposed in 2008.

N-Doped carbon coated bismuth nanorods with a hollow structure as an anode for superior-performance potassium-ion batteries.

Bismuth (Bi) is a promising anode material for potassium-ion batteries due to its high energy density. However, the large volume change limits its applications. Herein, N-doped carbon coated Bi nanorods with a hollow structure are fabricated and they exhibit excellent long-term cycling performance (88% capacity retention over 1000 cycles) and high-rate ability (297 mA h g-1 at 20C, 94% capacity of that at 1C). Furthermore, the mechanism was expounded by in situ XRD, indicating a multi-phase reaction for the initial discharge process and three two-phase reactions for the subsequent charge/discharge processes.

Conductive cobalt doped niobium nitride porous spheres as an efficient polysulfide convertor for advanced lithium-sulfur batteries

Porous Co-NbN spheres with excellent conductivity are used as sulfur hosts for lithium-sulfur batteries, which deliver excellent long-term cycle stability and performance with a high sulfur loading and lean electrolyte.

NaV6O15 microflowers as a stable cathode material for high-performance aqueous zinc-ion batteries

Reversible aqueous zinc-ion batteries (ZIBs) have great potential for large-scale energy storage owing to their low cost and safety. However, the lack of long-lifetime positive materials severely restricts the development of ZIBs. Herein, we report NaV6O15 microflowers as a cathode material for ZIBs with excellent electrochemical performance, including a high specific capacity of ∼300 mA h g−1 at 100 mA g−1 and 141 mA h g−1 maintained after 2000 cycles at 5 A g−1 with a capacity retention of ∼107%. The high diffusion coefficient and stable tunneled structure of NaV6O15 facilitate Zn2+ intercalation/extraction and long-term cycle stability.

Phase transformation and sulfur vacancy modulation of 2D layered tin sulfide nanoplates as highly durable anodes for pseudocapacitive lithium storage

Abstract Despite the fulfilling progress in fabricating metal chalcogenides-based battery electrodes, most effort focuses on construction of hybrid architectures and/or foreign elemental doping for improving electrochemical performance. In this work, we report a self-template strategy to synthesize hexagonal SnS2 and orthorhombic SnS nanoplates with abundant S vacancies as advanced anode materials of lithium-ion batteries (LIBs). Phase evolution from hexagonal SnS2 to orthorhombic SnS by thermal annealing is investigated. The resultant tin sulfide nanoplates featuring abundant S vacancies and decreased bandgaps can provide more active sites, higher Li+-ion diffusion mobility and better electronic conductivity, which are beneficial for improving electrochemical reaction kinetics. Consequently, both the S-vacancy-rich SnS2 (SVR-SnS2) and the SVR-SnS nanoplates show significantly enhanced cycling performance and rate capability compared with the interlayer-expanded SnS2 (IE-SnS2) nanoplates. Remarkably, the SVR-SnS nanoplates can exhibit outstanding rate capability (510 mAh g−1 at 10 A g−1) and excellent long-term cycling performance. A reversible capacity as high as 765 mAh g−1 at a high current of 2 A g−1 can be delivered even after 1200 cycles. It is the best cycling performance of SnS-based electrodes for LIBs to date. Besides the benefits from S vacancies, the pseudocapacitive contribution is also responsible for the fast and stable lithium storage capability. The present work provides a new strategy for modulating 2D layered tin sulfide nanoplates as promising anode materials for LIB applications.