Cross-Linked Gel Electrolytes with Self-Healing Functionalities for Smart Lithium Batteries.

Next-generation Li-ion batteries must guarantee improved durability, quality, reliability, and safety to satisfy the stringent technical requirements of crucial sectors such as e-mobility. One breakthrough strategy to overcome the degradation phenomena affecting the battery performance is the development of advanced materials integrating smart functionalities, such as self-healing units. Herein, we propose a gel electrolyte based on a uniform and highly cross-linked network, hosting a high amount of liquid electrolyte, with multiple advantages: (i) autonomous, fast self-healing, and a promising PF5-scavenging role; (ii) solid-like mechanical stability despite the large fraction of entrapped liquid; and (iii) good Li+ transport. It is shown that such a gel electrolyte has very good conductivity (>1.0 mS cm-1 at 40 °C) with low activation energy (0.25 eV) for the ion transport. The transport properties are easily restored in the case of physical damages, thanks to the outstanding capability of the polymer to intrinsically repair severe cracks or fractures. The good elastic modulus of the cross-linked network, combined with the high fraction of anions immobilized within the polymer backbone, guarantees stable Li electrodeposition, disfavoring the formation of mossy dendrites with the Li metal anode. We demonstrate the electrolyte performance in a full-cell configuration with a LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode, obtaining good cycling performance and stability.

Autonomous Self-Healing Strategy for Stable Sodium-Ion Battery: A Case Study of Black Phosphorus Anodes.

Autonomic self-healing (SH), namely, the ability to repair damages from mechanical stress spontaneously, is polarizing attention in the field of new-generation electrochemical devices. This property is highly attractive to enhance the durability of rechargeable Li-ion batteries (LIBs) or Na-ion batteries (SIBs), where high-performing anode active materials (silicon, phosphorus, etc.) are strongly affected by volume expansion and phase changes upon ion insertion. Here, we applied a SH strategy, based on the dynamic quadruple hydrogen bonding, to nanosized black phosphorus (BP) anodes for Na-ion cells. The goal is to overcome drastic capacity decay and short lifetime, resulting from mechanical damages induced by the volumetric expansion/contraction upon sodiation/desodiation. Specifically, we developed novel ureidopyrimidinone (UPy)-telechelic systems and related blends with poly(ethylene oxide) as novel and green binders alternative to the more conventional ones, such as polyacrylic acid and carboxymethylcellulose, which are typically used in SIBs. BP anodes show impressively improved (more than 6 times) capacity retention when employing the new SH polymeric blend. In particular, the SH electrode still works at a current density higher than 3.5 A g-1, whereas the standard BP electrode exhibits very poor performances already at current densities lower than 0.5 A g-1. This is the result of better adhesion, buffering properties, and spontaneous damage reparation.

Photosynthetic microbial fuel cell with polybenzimidazole membrane: synergy between bacteria and algae for wastewater removal and biorefinery.

Here, we demonstrate a very efficient simultaneous approach of bioenergy generation from wastewater and added-value compounds production by using a photosynthetic microalgae microbial fuel cells (PMFC), based on polybenzimidazole (PBI) composite membrane as separator. The use of PBI was proved to be very promising, even more convenient than Nafion™ in terms of energy performances as well as cost and sustainability. This polymer is also easily autoclavable, so allowing a re-use of the separator with a consequent beneficial cost effect. Two PMFCs were investigated: 1) Pt electrocatalysed and 2) Pt-free. They were operated as microbial carbon capture (MCC) device under continuous illumination, by using a domestic wastewater as anolyte and Scenedesmus acutus strain in the catholyte. The Pt-based cell allowed to generate higher volumetric power density (∼400 mW m-3) after more than 100 operating days. This resulted in an improved wastewater treatment efficiency, determined in terms of normalised energy recovery (NER > 0.19 kWh kgCOD-1 in case of Pt). The CO2 fixation of the PMFC-grown microalgae leaded to a high accumulation of added-value products, namely pigments and fatty acids. A significant quantity of lutein was observed as well as a relevant amount of other valuable carotenoids, as violaxanthin, astaxanthin and cantaxanthin. The lipids were even excellently accumulated (49%dw). Their profile was mainly composed by fatty acids in the range C16-18, which are particularly indicated for the biofuel production. These results demonstrate the feasibility and the implemented sustainability of such PMFCs as a great potential technology for the wastewater treatment and the simultaneous production of valuable products.

Energy harvesting from human motion: materials and techniques.

Energy harvesting from human motion is a research field under rapid development. In this tutorial review we address the main physical and physico-chemical processes which can lead to energy generation, including electromagnetism, piezoelectricity, and electrostatic generation. Emphasis is put on the relationships among material properties and device efficiency. Some new and relatively less known approaches, such as triboelectric nanogeneration (TENG) and reverse electrowetting (REWOD), are reported in more detail.

Silica-polyethylene glycol hybrids synthesized by sol-gel: Biocompatibility improvement of titanium implants by coating.

Although metallic implants are the most used in dental and orthopaedic fields, they can early fail due to low tissue tolerance or osseointegration ability. To overcome this drawback, functional coatings can be applied on the metallic surface to provide a firm fixation of the implants. The objective of the present study was twofold: to synthesize and to characterize silica/polyethylene glycol (PEG) hybrid materials using sol-gel technique and to investigate their capability to dip-coat titanium grade 4 (Ti-gr4) substrates to improve their biological properties. Various hybrid systems have been synthesized by changing the ratio between the organic and inorganic phases in order to study the influence of the polymer amount on the structure and, thus, on the properties of the coatings. Fourier transform infrared (FTIR) spectroscopy and solid state Nuclear Magnetic Resonance (NMR) allowed us to detect the formation of hydrogen bonds between the inorganic sol-gel matrix and the organic component. SEM analysis showed that high PEG content enables to obtain crack free-coating. Moreover, the effective improvement in biological properties of Ti-gr4 implants has been evaluated by performing in vitro tests. The bioactivity of the hybrid coatings has been showed by the hydroxyapatite formation on the surface of SiO2/PEG coated Ti-gr4 substrates after soaking in a simulated body fluid and the lack of cytotoxicity by the WST-8 Assay. The results showed that the coated substrates are more bioactive and biocompatible than the uncoated ones and that the bioactivity is not significantly affected by PEG amount whereas its addition makes the films more biocompatible.

Nature of conductivity in SrSiO3-based fast ion conductors.

In this paper we report the preparation and characterization of Sr1-xNaxSiO3-0.5x samples, recently proposed as oxide ion conductors. We show that Na-doping unlikely takes place in the silicate phase, and that a secondary glassy phase is at the origin of the transport properties, thereby suggesting that the conductivity is due only to a limited extent to oxide ion migration in the crystalline system.

Synthesis of zirconia/polyethylene glycol hybrid materials by sol-gel processing and connections between structure and release kinetic of indomethacin.

Controlled and local drug delivery systems of anti-inflammatory agents are attracting an increasing attention because of their extended therapeutic effect and reduced side effects. In this work, the sol-gel process was used to synthesize zirconia/polyethylene glycol (ZrO2/PEG) hybrid materials containing indomethacin for controlled drug delivery. Different percentages of PEG were introduced in the synthesis to modulate the release kinetic and an exhaustive chemical characterization of all samples was performed to detect the relationship between their structure and release ability. Fourier transform spectroscopy and solid-state NMR show that the Zr-OH groups of the inorganic matrix bond both the ethereal oxygen atoms of the polymer and the carboxylic groups of the drug. X-ray diffraction analysis ascertains the amorphous nature of those materials. Scanning electron microscopy detects the nanostructure and the homogeneous morphology of the synthesized materials. The bioactivity was demonstrated by the formation of a hydroxyapatite layer on the surface of the samples, after soaking in a simulated body fluid. The release kinetics study, performed by HPLC UV-Vis spectroscopy, proves that the release ability depends on PEG and the drug amount and also demonstrates the indomethacin integrity after the synthetic treatment.

Effects of water-soluble functionalized multi-walled carbon nanotubes examined by different cytotoxicity methods in human astrocyte D384 and lung A549 cells.

The widespread projected use of functionalized carbon nanotubes (CNTs) makes it important to understand their potential harmful effects. Two cell culture systems, human A549 pneumocytes and D384 astrocytoma cells, were used to assess cytotoxicity of multi-walled CNTs (MWCNTs) with varying degrees of functionalization. Laboratory-made highly functionalized hf-MW-NH(2) and less functionalized CNTs (MW-COOH and MW-NH(2)) were tested in comparison with pristine MWCNTs, carbon black (CB) and silica (SiO(2)) by MTT assay and calcein/propidium iodide (PI) staining. Purity and physicochemical properties of the test nanomaterials were also determined. In both MTT and calcein/PI assays, highly functionalized CNTs (hf-MW-NH(2)) caused moderate loss of cell viability at doses >or=100 microg/ml being apparently less cytotoxic than SiO(2). In preparations treated with CB or the other nanotube types (pristine MWCNTs, MW-COOH and the less functionalized amino-substituted MW-NH(2)) the calcein/PI test indicated no loss of cell viability, whereas MTT assay apparently showed apparent cytotoxic response, occurring not dose-dependently at exceedingly low CNT concentrations (1 microg/ml). The latter nanomaterials were difficult to disperse showing higher aggregate ranges and tendency to agglomerate in bundle-like form in cell cultures. In contrast, hf-MW-NH(2) were water soluble and easily dispersible in medium; they presented lower aggregate size range as well as considerably lower length to diameter ratios and low tendency to form aggregates compared to the other CNTs tested. The MTT data may reflect a false positive cytotoxicity signal possibly due to non-specific CNT interaction with cell culture components. Thus, these properties obtained by chemical functionalization, such as water solubility, high dispersibility and low agglomeration tendency were relevant factors in modulating cytotoxicity. This study indicates that properties obtained by chemical functionalization, such as water solubility, high dispersibility and low agglomeration tendency are relevant factors in modulating cytotoxicity of CNTs.

Cation distribution in LiMgVO4 and LiZnVO4: structural and spectroscopic study.

The room temperature cation occupancy in LiMgVO(4) and LiZnVO(4) crystallographic sites is obtained by means of the combined use of X-ray powder diffraction (XRPD), (7)Li and (51)V magic angle spinning nuclear magnetic resonance (MAS NMR), and micro-Raman measurements. In the LiMgVO(4) Cmcm orthorhombic structure, the 4c (C(2)(v) symmetry) tetrahedral vanadium site is fully ordered; on the contrary, the Li 4c tetrahedral site and the 4b (C(2)(h) symmetry) Mg octahedral site display about 22% of reciprocal cationic exchange. Higher cationic disorder is observed in LiZnVO(4): the three cations can distribute on the three tetrahedral and distinct sites of the R-3 structure. XRPD and MAS NMR analysis results highly agree for what concerns vanadium ion distribution on the three cationic sites (about 25, 26, and 47%). From the full profile fitting of XRPD patterns with the Rietveld method, it is also obtained that Li(+) displays a slightly preferred occupation of the T1 position (approximately 55%) and Zn(2+) of the T2 position (approximately 46%). The vibrational spectra of the two compounds are characterized by different peak positions and broadening of the Raman modes, reflecting the cation distribution and the local vibrational unit distortion. A comparison is also made with recent Raman results on Li(3)VO(4). High temperature XRPD measurements rule out possible structural transitions up to 673 K for both compounds.

Transport and structural properties of pure and Cr doped Li3VO4.

This study deals with the effects of 5 and 10% chromium additions on the transport and structural properties of Li3VO4. The Cr substitution is easily obtained without impurity phases and does not affect the room- and high-temperature host crystal structure, as evidenced by X-ray powder diffraction and micro-Raman analysis. The EPR signals are interpreted in terms of quantified amounts of Cr ions in 5+ and 3+ valence states. Suitable 7Li and 51V MAS NMR spectra simulations agree with the EPR results about the relative amount of Cr5+ and Cr3+ ions substituted in V5+ and Li+ sites, respectively. The Cr3+ presence on Li site, also suggested by Raman results and Rietveld refinements, requires Li vacancies to maintain the charge neutrality. The p-type conductivity, suggested by the positive thermoelectric power coefficients, significantly increases by the cation doping up to an order of magnitude.

Biological effects of magnetic fields.

The literature about the biological effects of magnetic fields is reviewed. We begin by discussing the weak and/or time variable fields, responsible for subtle changes in the circadian rhythms of superior animals, which are believed to be induced by same sort of "resonant mechanism". The safety issues related with the strong magnetic fields and gradients generated by clinical NMR magnets are then considered. The last portion summarizes the debate about the biological effects of strong and uniform magnetic fields.

Synthesis of magnetic gradients for NMR tomography.

A numerical method is applied to calculate an optimal distribution of currents in air which generate the magnetic field gradients required to spatially encode the radiofrequency signal in a NMR tomographic experiment. We compare the performances of the gradient circuits for the whole body air-core electromagnet described by Bangert and Mansfield (J. Phys. E 15; 1982) with the results of our optimization.