Spray-Printed Flexible Li2S Cathode with Inorganic Ion-Conductive Binder Nano-Li3PS4.

Flexible solid-state batteries fabricated by printing techniques are promising integrated power supplies for miniaturized and customized electronic devices. While typically these batteries use polymer solid electrolytes, a flexible Li2S cathode with sulfide solid electrolyte is spray-printed in this work, by using solvated Li3PS4 nanoparticles as inorganic ion-conductive binder. This benefits from a novel low-temperature-sintering property of these nanoparticles, which can be pressure-free densified, along with the desolvation process, and thus bind the cathode at 250 °C. The battery can be stably charged and discharged for 300 cycles with no stacking pressure, and the capacity maintains at 840 mA h gLi2 S-1. We believe this low-temperature-sintering phenomenon of solid electrolyte nanoparticles will open a new path toward the application of sulfide solid electrolytes in printed solid-state batteries.

The Voltage-Adaptive Effect in Lithium-Sulfur Batteries Integrated with an Electron-Conductive Interlayer.

Lithium-sulfur (Li-S) batteries are considered as one of the top competitors to go beyond Li-ion batteries. However, the shuttle effect triggered by soluble lithium polysulfides (LPSs) brings great troubles for understanding the solid-liquid-solid conversion process of the sulfur cathode. Herein, a new characterization technique is developed to deepen the understanding of such soluble LPSs shuttling, by integrating an electron-conductive interlayer. The voltage of the interlayer exhibits a voltage-adaptive effect to the cathode, indicating the true dependence of the open-circuit voltages on the LPSs instead of on the solid cathodes. Furthermore, a quantitative method can be introduced to monitor the shuttling LPSs by such interlayer design, and it shows great potential to be a new standard technique, providing direct comparison of the shuttle effect between different studies. The newly developed interlayer design paves an avenue to gain new insight into the reaction process and improve the performance of Li-S batteries.

Improving Cycling Stability of the Lithium Anode by a Spin-Coated High-Purity Li3PS4 Artificial SEI Layer.

Controlling the composition and microstructure of the solid electrolyte interphase (SEI) layer is critical to improving the cycling stability of the high-energy-density lithium-metal electrode. It is a quite tricky task to control the properties of the SEI layer which is conventionally formed by the chemical reactions between a Li metal and the additives. Herein, we develop a new route to synthesize a lithium-compatible sol of the sulfide electrolyte Li3PS4, so that a Li3PS4 artificial SEI layer with a controllable nanoscale thickness and high phase purity can be prepared by spin-coating. The layer stabilizes the lithium/electrolyte interface by homogenizing the Li-ion flux, preventing the parasitic reactions, and alleviating concentration polarization. Consequently, a symmetrical cell with the Li3PS4-modified lithium electrodes can achieve stable lithium plating/stripping for 800 h at a current density of 1 mA cm-2. The Li-S batteries assembled with the Li3PS4-protected Li anodes show better capacity retention than their bare Li counterparts, whose average decay rate from the 240th cycle to the 800th cycle is only 0.004%/cycle. In addition, the Li3PS4 layer improves the rate capacity of the batteries, significantly enhancing the capacity from 175 to 682 mA h g-1 at a 2 C rate. The spin-coated Li3PS4 artificial SEI layer provides a new strategy to develop high-performance Li metal batteries.

Stabilizing Interface between Li2S-P2S5 Glass-Ceramic Electrolyte and Ether Electrolyte by Tuning Solvation Reaction.

Using solid-liquid hybrid electrolytes is an effective strategy to overcome the large solid/solid interfacial resistance in all-solid-state batteries and the safety problems in liquid batteries. The properties of the solid/liquid electrolyte interphase layer (SLEI) are essential for the performance of solid-liquid hybrid electrolytes. In this work, the solvation reactions between Li2S-P2S5 glass-ceramic solid electrolytes (SEs) and ether electrolytes were studied, and their influence on the SLEI was examined. Although 1,2-dimethoxyethane (DME) reacted with the Li2S-P2S5 glass-ceramic SE to form a dense SLEI, 1,3-dioxolane (DOL) severely corroded the SE, resulting in a loose SLEI. Consequently, a stable SLEI formed with DME. Using a combination of the Li2S-P2S5 glass-ceramic SE and the DME-based liquid electrolyte (LE), stable lithium plating/stripping cycles over 1000 h and a hybrid Li-S battery that retained a specific capacity of 730 mAh g-1 after 200 cycles were demonstrated. The knowledge of the reactions between the sulfide electrolytes and the organic LEs is instructive for the design of stable sulfide-liquid hybrid electrolytes for advanced batteries.

Improved antifouling properties of PVA hydrogel via an organic semiconductor graphitic carbon nitride catalyzed surface-initiated photo atom transfer radical polymerization.

An innovative g-C3N4 catalyzed surface-initiated photo atom transfer radical polymerization (SI-photoATRP) has been developed to construct MEDSAH zwitterionic polymer brushes on PVA hydrogel surface. g-C3N4 catalyzed SI-photoATRP is temporal and spatial control. As a heterogeneous reaction system, it can solve the catalyst residues problem. After grafting with MEDSAH, surface chemical composition and morphology of PVA-g-pMEDSAH hydrogel confirmed that MEDSAH was successfully grafted onto PVA hydrogel. Thermal property of PVA-g-pMEDSAH hydrogel decreased and hydrophilicity increased. No statistically significant differences between PVA and PVA-g-pMEDSAH were observed on mechanical properties. Cytotoxicity in vitro of PVA-g-pMEDSAH hydrogel could be considered as no cytotoxicity for L929 and NDHF cells. The antifouling properties of PVA-g-pMEDSAH hydrogel were significantly improved due to the enhancement of the surface hydration and steric repulsion effects caused by pMEDSAH polymer brushes. In addition, g-C3N4 is easier to modify to enhance the photocatalyst property. Thus, the heterogeneous reaction system of g-C3N4 catalyzed SI-photoATRP has huge potential applied in biomaterials surface modification.

Surface Fluorination Modification and Anti-Biofouling Study of a pHEMA Hydrogel.

A poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel film was prepared by bulk polymerization. Then, it was surface modified by perfluorooctanoyl chloride to improve the anti-biofouling properties. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDXS), and atomic force microscopy (AFM) analyses demonstrated that the uniform dense fluorinated layer had been successfully grafted onto pHEMA. The water contact angle (WCA) of the modified pHEMA film increased to 135°, while the surface energy decreased to 13.32 mN/m. The protein and bacterial adhesion properties of the modified pHEMA were decreased significantly. The in vitro cytotoxicity showed that the modified pHEMA was noncytotoxic. Thus, the fluorinated modification on the material surface was a convenient and effective method to establish a hydrophobic and anti-biofouling surface.

Will Sulfide Electrolytes be Suitable Candidates for Constructing a Stable Solid/Liquid Electrolyte Interface?

Conversion-type batteries with electrode materials partially dissolved in a liquid electrolyte exhibit high specific capacity and excellent redox kinetics, but currently poor stability due to the shuttle effect. Using a solid-electrolyte separator to block the mass exchange between the cathode and the anode can eliminate the shuttle effect. A stable interface between the solid-electrolyte separator and the liquid electrolyte is essential for the battery performance. Here, we demonstrate that a stable interface with low interfacial resistance and limited side reactions can be formed between the sulfide solid-electrolyte ß-Li3PS4 and the widely used ether-based liquid electrolytes, under both reduction and oxidation conditions, due to the rapid formation of an effective protective layer of ether-solvated Li3PS4 at the sulfide/liquid electrolyte interface. This discovery has inspired the design of a ß-Li3PS4-coated solid-electrolyte Li7P3S11 separator with a simultaneously high ion-conduction ability and good interfacial stability with the liquid electrolyte, so that hybrid lithium-sulfur (Li-S) batteries with this composite separator conserve a high discharge capacity of 1047 mA h g-1 and a high second discharge plateau of 2.06 V after 150 cycles.

Enhancing antifouling property of PVA membrane by grafting zwitterionic polymer via SI-ATRP method.

Poly(zwitterions) polymer brushes were fabricated by surface-initiated atom transfer radical polymerization (SI-ATRP) on PVA substrate. The results of XPS and FTIR proved the successful graft of CBMA and SBMA to PVA. The surface of the PVA films would be rougher after the functionalization. Its hydrophilicity increased dramatically and the water contact angle decreased from 45.2° to 7.2°. The visible light transmittance was above 88%. Mechanical properties decreased slightly after grafting, the tensile strength and tensile strain at break were in 1.23-1.85 MPa and 361.7-471.1%, respectively. The anti-protein adsorption performance of the modified PVA film was significantly enhanced and the lowest adsorption amount was up to 2.25 µg/cm2. The cytotoxicity grade of modified PVA film was 0-1, which indicated the modified film possessed no cytotoxicity. Additionally, the surface of zwitterion-grafted PVA film had strongly resistance to cell adhesion. All the results confirmed that the zwitterions modified PVA was a promising anti-fouling material for the further biomedical use.

Hierarchical Mesoporous/Macroporous Co-Doped NiO Nanosheet Arrays as Free-Standing Electrode Materials for Rechargeable Li-O2 Batteries.

Lithium-oxygen (Li-O2) batteries have been widely recognized as appealing power systems for their extremely high energy density versus common Li-ion batteries. However, there are still lots of issues that need to be addressed toward the practical application. Here, free-standing Co-doped NiO three-dimensional nanosheets were prepared by a hydrothermal synthesis method and directly employed as the air-breathing cathode of the Li-O2 battery. The morphological phenomenon and electrochemical performance of the as-prepared cathode material were characterized by high-resolution scanning electron microscopy, X-ray diffraction, cyclic voltammetry, galvanostatic charge-discharge tests, and electrochemical impedance spectroscopy measurements. The Co-doped NiO electrode delivered a maximum discharge capacity of around 12 857 mA h g-1 with a low overpotential (0.82 V) at 200 mA g-1. Under upper-limit specific capacities of 500 mA h g-1 at 400 mA g-1, the Li-O2 batteries exhibited a long cycle life of 165 cycles. Compared with the undoped NiO electrode, the Li-O2 battery based on the Co-doped NiO cathode showed significantly higher oxygen reduction reaction and oxygen evolution reaction activities. This superior electrochemical performance is because of the partial substitution of Ni2+ in the NiO matrix by Co2+ to improve the p-type electronic conductivity of NiO. In addition, the morphology and specific surface area of NiO are affected by Co doping, which can expand the electrode-electrolyte contact area and lead to sufficient space for Li2O2 deposition. This approach harnesses the great potential of Co-doped NiO nanosheets for practical applications as advanced electrodes for rechargeable Li-O2 batteries.

Genipin-crosslinked polyvinyl alcohol/silk fibroin/nano-hydroxyapatite hydrogel for fabrication of artificial cornea scaffolds-a novel approach to corneal tissue engineering.

Design of artificial corneal scaffolds substitute is crucial for replacement of impaired cornea. In this paper, porous polyvinyl alcohol/silk fibroin/nano-hydroxyapatite (PVA/SF/n-HA) composite hydrogel was prepared via the genipin (GP) cross-linking, the pore diameter of the hydrogel ranged from 8.138 nm and 90.269 nm, and the physical and physiological function of hydrogel were investigated. The resulting hydrogel exhibited favourable physical properties. With the GP content increasing, the structural regularity of PVA/SF/n-HA composite hydrogel was enhanced and the thermal stability was improved. The moisture content was slightly decreased and generally maintained at approximately 70%. The tensile strength was heightened up to 0.64 MPa, while the breaking elongation was decreased slightly. Moreover, the biofunction was investigated. The in vitro degradation test demonstrated that with the addition of GP, the stability of the composite hydrogels in protease XIV solution was promoted and the three-dimensional porosity structure of composite hydrogels was maintained as ever. And the human corneal fibroblasts (HCFs) were employed to examine the cells cytotoxicity of the PVA/SF/n-HA composite hydrogels with different GP content by CCK-8 assay. Based on confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM), HCFs had individually commendable adhesion and proliferation on PVA/n-HA/SF composite hydrogel. HCFs proliferated and grew into the pores of composite hydrogel. The results of biocompatibility experiments of composite hydrogel suggested that it was no acute toxicity, in vitro cytotoxicity was 0 or 1 grade. Overall, results from this paper, PVA/n-HA/SF composite hydrogel was a qualified medical material which conformed to the national standard, could be a promising alternative for artificial cornea scaffold material-a novel approach to corneal tissue engineering.

Hydrophilic modification on polyvinyl alcohol membrane by hyaluronic acid.

PVA was dissolved in mixed solvent (DMSO and water) and followed by several freeze-thaw cycles in a mold to produce PVA membrane. Surface modification of PVA membranes by HA molecules was investigated to improve the hydrophilicity of the membrane surface thereby reducing adsorption of the proteins onto the membrane. The surface composition, water contact angle, optical and mechanical properties, surface morphology, cell compatibility and protein adhesion were systematically investigated. ATR-FTIR spectra, XPS, SEM and AFM indicated that PVA membranes were successfully modified by grafting of the HA. The modified membranes showed increased hydrophilicity and cytocompatibility, decreased surface roughness and mechanical properties, and suppressed cell and protein adhesion compared to the pristine membrane. In general, the achievement of the HA coating with anti-adhesive property can potentially be widely used on surface modification of artificial cornea and other biomedical implants.

Hydroxyl terminated mesoporous silica-assisted dispersion of ligand-free CsPbBr3/Cs4PbBr6 nanocrystals in polymer for stable white LED.

Composite nanocrystals of CsPbBr3/Cs4PbBr6 have gained significant attention because of their high stability and unique photoelectronic property. However, their dispersion within polymers is rather difficult due to the absence of ligands, which limits further enhancement of stability and practical applications. Herein, a feasible, effective, and general method was developed to assist the dispersion of CsPbBr3/Cs4PbBr6 nanocrystals in polymer by using -OH terminated mesoporous silica as a micro-container. The composite film obtained is employed as the light emitter for the fabrication of white LEDs. It was found that silica loaded with composite nanocrystals disperse uniformly in the composite film which shows excellent stability with a half-life of 400 hours under the illumination with optical power density of 1.7 × 103 mW cm-2 and peak wavelength of 457 nm. The inner pore of the micro-container attracts precursors and confines the crystallization, leading to the incorporation of CsPbBr3/Cs4PbBr6 nanocrystals. Meanwhile, the hydrogen bonding of the outer surface with poly(methyl methacrylate) (PMMA) enables good dispersion of the loaded micro-containers in PMMA as evidenced by the optical microscopy characterization and water resistance test. Moreover, this strategy can also be applied to other kinds of polymers since the outside -OH group can react with siliane coupling agents. On the basis of stability tests associated with silica and polymer encapsulation, a possible mechanism is proposed for the enhancement of the stability of composite films under working condition.

Charge injection based electrical stimulation on polypyrrole planar electrodes to regulate cellular osteogenic differentiation.

In this study, polypyrrole (Ppy) electrodes were prepared to support an electrical stimulation to MC3T3-E1 cells for regulating their osteogenic differentiation. The charge injection capacity (C Q) of the Ppy electrodes could be adjusted by the Ppy thickness, and a higher C Q could make the electrode able to produce a higher charge injection quantity (Q inj) at applied voltage. The Q inj onto electrode could be considered as the intensity of the stimulation pulse to cells, and the pulse frequency means the number of electric stimulation with Q inj at one second. Hence, we conducted the present work in the view of Q inj. When the cells were electrically stimulated for 1 hour per day, the electrodes with Q inj ranged in 0.08-0.15 µQ had an obvious role in enhancing cellular osteogenic differentiation whereas Q inj of lower than 0.03 µQ or more than 0.30 µQ gave the stimulations with no or negative effects. And the stimulation with 1 or 25 Hz showed to enhance the differentiation, whereas the stimulation with 50 Hz gave an inhibiting effect. We further found the osteogenic differentiation potential triggered by electrical simulation was related to cell growth stage, and the stimulation carried out at early stage (day 2-5) during 8 days cell culture showed more contribution to enhancing osteogenic differentiation than that at later stage (day 6-8). It is proposed that the desired stimulation effects require that an appropriate voltage-gated calcium ion channel and efficient intracellular calcium ion oscillation are well activated. This work therefore reveals Q inj as an important electrode parameter to decide effective simulations and provides an insight into understanding of the role of electrode material characters in regulating cellular osteogenic differentiation during stimulation.

Mediation of cellular osteogenic differentiation through daily stimulation time based on polypyrrole planar electrodes.

In electrical stimulation (ES), daily stimulation time means the interacting duration with cells per day, and is a vital factor for mediating cellular function. In the present study, the effect of stimulation time on osteogenic differentiation of MC3T3-E1 cells was investigated under ES on polypyrrole (Ppy) planar interdigitated electrodes (IDE). The results demonstrated that only a suitable daily stimulation time supported to obviously upregulate the expression of ALP protein and osteogenesis-related genes (ALP, Col-I, Runx2 and OCN), while a short or long daily stimulation time showed no significant outcomes. These might be attributed to the mechanism that an ES induced transient change in intracellular calcium ion concentration, which was responsible for activating calcium ion signaling pathway to enhance cellular osteogenic differentiation. A shorter daily time could lead to insufficient duration for the transient change in intracellular calcium ion concentration, and a longer daily time could give rise to cellular fatigue with no transient change. This work therefore provides new insights into the fundamental understanding of cell responses to ES and will have an impact on further designing materials to mediate cell behaviors.

Facile synthesis and enhanced electrochemical properties of reduced graphene oxide/MoS2/polyaniline ternary composites.

In this study, ternary composites of reduced graphene oxide/molybdenum disulfide/polyaniline (rGEO/MoS2/PANI) were prepared via a two-stage facile synthesis including a hydrothermal reaction and polymerization at room temperature which makes the materials much easier for industrialization. The doping of reduced graphene oxide (rGEO) decreases the aggregation of MoS2 and enhances the electronic conductivities of MoS2, thus exhibiting better capacitance properties (531 F g-1 at 1 A g-1) and cycling stabilities (86.7% retained capacitance over 3000 cycles at 1 A g-1) of ternary composites than a uniform material (MoS2) or binary materials (MoS2/PANI). The combined effects between the three components make the composites obtain both pseudocapacitance and double-layer capacitance, which can be used to explain the improvement of electrochemical performances.

Mechanical properties and in vivo study of modified-hydroxyapatite/polyetheretherketone biocomposites.

Polyether ether ketone (PEEK) has received much attention for its excellent mechanical properties and biocompatibility. Here, the silane coupling agent KH560 [γ-(2,3-epoxypropoxy)propyltrimethoxysilane] is used for graft modification of bioactive HA (hydroxyapatite) particles and for preparing HA/PEEK composites via a hot-press molding method. The prepared HA/PEEK composites were tested for their mechanical properties with SEM (scanning electron microscopy), infrared spectroscopy, and thermo-analysis. The results show that silane coupling KH-560 modifies HA successfully and that the tensile strengths of HA/PEEK and m-HA/PEEK composites indicate an increasing and then a decreasing tendency with increasing HA contents. The non-modified HA/PEEK composites display the same trend as the modified specimens with lower tensile strength and consist of sharp points. When the HA content is 5wt.%, the tensile strength of m-HA/PEEK composite reaches its maximum, which is 23% higher than that of pure PEEK specimens. The in vivo experiments of m-HA/PEEK used a biomechanical push-out test, SEM, optical microscopy, and an Image-Pro Express C image analysis system. The growth of the bone tissues around the m-HA/PEEK composites with an HA content of 5wt.% is better than that of specimens with different HA contents. This finding shows the nano-scale effect of the bioactive filler HA in PEEK substrates, which obviously contributes to the growth of the surrounding bone issues in vivo. This study could provide theoretical support for the further promotion and application of high-performance engineering plastics such as PEEK in biomedical fields.

Study on the Mixed Electrolyte of N,N-Dimethylacetamide/Sulfolane and Its Application in Aprotic Lithium-Air Batteries.

Aprotic lithium-air batteries have recently drawn considerable attention due to their ultrahigh specific energy. However, the chemical and electrochemical instability of the electrolyte is one of the most critical issues that need to be overcome. To increase the stability and maintain a relatively high conductivity of the lithium ion, a mixed electrolyte of sulfolane (TMS) and N,N-dimethylacetamide (DMA) was evaluated and tested in an aprotic lithium-air battery. The physical and chemical characterizations showed that the mixed electrolyte exhibited a relatively low viscosity, high ionic conductivity and oxygen solubility, and good stability. In addition, it was found that lithium-air batteries with an optimized electrolyte composition (DMA/TMS = 20:80, % v/v) showed a better cycle life and lower charge overpotential as compared to those with electrolytes with a single solvent, either DMA or TMS.

Sonochemical synthesis of cobalt aluminate nanoparticles under various preparation parameters.

Cobalt aluminate (CoAl(2)O(4)) nanoparticles were synthesized using a precursor method with the aid of ultrasound irradiation under various preparation parameters. The effects of the preparation parameters, such as the sonochemical reaction time and temperature, precipitation agents, calcination temperature and time on the formation of CoAl(2)O(4) were investigated. The precursor on heating yields nanosized CoAl(2)O(4) particles and both these nanoparticles and the precursor were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The use of ultrasound irradiation during the homogeneous precipitation of the precursor reduces the duration of the precipitation reaction. The mechanism of the formation of cobalt aluminate was investigated by means of Fourier transformation infrared spectroscopy (FT-IR) and EDX (energy dispersive X-ray). The thermal decomposition process and kinetics of the precursor of nanosized CoAl(2)O(4) were investigated by means of differential scanning calorimetry (DSC) and thermogravimetry (TG). The apparent activation energy (E) and the pre-exponential constant (A) were 304.26 kJ/mol and 6.441 x 10(14)s(-1), respectively. Specific surface area was investigated by means of Brunauer Emmett Teller (BET) surface area measurements.

Effect of processing conditions on sonochemical synthesis of nanosized copper aluminate powders.

Nanosized copper aluminate (CuAl(2)O(4)) spinel particles have been prepared by a precursor approach with the aid of ultrasound radiation. Mono-phasic copper aluminate with a crystallite diameter of 17nm along the (311) plane was formed when the products were synthesized using Cu(NO(3))(2) x 6H(2)O and Al(NO(3))(3) x 9H(2)O as starting materials, with urea as a precipitation agent at a concentration of 9M. The reaction was carried out under ultrasound irradiation at 80 degrees C for 4h and a calcination temperature of 900 degrees C for 6h. The synthesized copper aluminate particles and the effect of different processing conditions such as the copper source, precipitation agents, sonochemical reaction time, calcination temperature and time were analyzed and characterized by the techniques of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and Fourier transformation infrared spectroscopy (FT-IR).