Lithium-ion Transport Properties in DMSO and TEGDME: Exploring the Influence of Solvation through Molecular Dynamics and Experiments.

This study explores the properties of aprotic electrolytes via the application of experimental methods, including nuclear magnetic resonance spectroscopy and electrochemical techniques, along with molecular dynamic modeling. The aim is to provide a quantitative description of the physico-chemical properties of two well-established electrolytes (case studies), each exhibiting significantly distinct dielectric properties: a LiTFSI (Lithium bis(trifluoromethanesulfonyl)imide) solution in dimethyl sulfoxide (DMSO, dielectric constant = 46.68) and a LiTFSI solution in tetraethylene glycol dimethyl ether (TEGDME, =7.71). We obtained a comprehensive insight into the properties of the electrolytes at both the macroscopic-collective and molecular levels with particular emphasis on the interactions between the Li ions and solvent molecules. We discovered remarkable disparities in the structural arrangements, solvation behaviors, and bulk-related properties of these electrolyte systems, particularly in response to temperature changes.

Understanding the Role of Imide-Based Salts and Borate-Based Additives for Safe and High-Performance Glyoxal-Based Electrolytes in Ni-Rich NMC811 Cathodes for Li-Ion Batteries.

Herein, the design of novel and safe electrolyte formulations for high-voltage Ni-rich cathodes is reported. The solvent mixture comprising 1,1,2,2-tetraethoxyethane and propylene carbonate not only displays good transport properties, but also greatly enhances the overall safety of the cell thanks to its low flammability. The influence of the conducting salts, that is, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(fluorosulfonyl)imide (LiFSI), and of the additives lithium bis(oxalato)borate (LiBOB) and lithium difluoro(oxalato)borate (LiDFOB) is examined. Molecular dynamics simulations are carried out to gain insights into the local structure of the different electrolytes and the lithium-ion coordination. Furthermore, special emphasis is placed on the film-forming abilities of the salts to suppress the anodic dissolution of the aluminum  current collector and to create a stable cathode electrolyte interphase (CEI). In this regard, the borate-based additives significantly alleviate the intrinsic challenges associated with the use of LiTFSI and LiFSI salts. It is worth remarking that a superior cathode performance is achieved by using the LiFSI/LiDFOB electrolyte, displaying a high specific capacity of 164 mAh g-1 at 6 C and ca. 95% capacity retention after 100 cycles at 1 C. This is attributed to the rich chemistry of the generated CEI layer, as confirmed by ex situ X-ray photoelectron spectroscopy.

Enhancement of Li/S Battery Performance by a Modified Reduced Graphene Oxide Carbon Host Decorated with MoO3.

Electrochemical energy storage systems based on sulfur and lithium can theoretically deliver high energy with the further benefit of low cost. However, the working mechanism of this device involves the dissolution of sulfur to high-molecular weight lithium polysulfides (LiPs with general formula Li2Sn, n≥4) in the electrolyte during the discharge process. Therefore, the resulting migration of partially dissociated LiPs by diffusion or under the effect of the electric field to the lithium anode, activates an internal shuttle mechanism, reduces the active material and in general leads to loss of performance and cycling stability. These drawbacks poses challenges to the commercialization of Li/S cells in the short term. In this study, we report on the decoration of reduced graphene oxide with MoO3 particles to enhance interactions with LiPs and retain sulfur at the cathode side. The combination of experiments and density functional theory calculations demonstrated improvements in binding interactions between the cathode and sulfur species, enhancing the cycling stability of the Li/S cells.

Improved Compatibility of α-NaMnO2 Cathodes at the Interface with Ionic Liquid Electrolytes.

The behaviour and compatibility of monoclinic sodium manganite, α-NaMnO2, cathodes at the interface with electrolytes based on the 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIFSI) and N-trimethyl-N-butylammonium bis(fluorosulfonyl)imide (N1114FSI) ionic liquids is presented and discussed. The Na+ insertion process was analysed through cyclic voltammetry tests combined with impedance spectroscopy measurements and the cell performance was tested by charge-discharge cycles. XPS and FIB-SEM measurements allowed analysis of the surface composition and the morphology of post-mortem cathodes. Overall, the α-NaMnO2 cathode showed high reversibility in N1114FSI-based electrolyte, delivering 60 % of the initial capacity after 1200 cycles in conjunction with a Coulombic efficiency above 99 %. To our knowledge, these very promising results are the best result obtained till now for monolithic α-NaMnO2 cathodes, are ascribable to the formation of a stable passive layer onto the electrode surface, as confirmed by spectroscopic analysis.

Semitransparent Organic Photovoltaic Devices: Interface/Bulk Properties and Stability Issues.

In the present work, an insight on the morpho/structural properties of semitransparent organic devices for buildings' integrated photovoltaics is presented, and issues related to interface and bulk stability are addressed. The organic photovoltaic (OPV) cells under investigation are characterized by a blend of PM6:Y6 as a photo-active layer, a ZnO ETL (electron transporting layer), a HTL (hole transporting layer) of HTL-X and a transparent electrode composed by Ag nanowires (AgNWs). The devices' active nanomaterials, processed as thin films, and their mutual nanoscale interfaces are investigated by a combination of in situ Energy Dispersive X-ray Reflectometry (EDXR) and ex situ Atomic Force Microscopy (AFM), X-ray Diffraction (XRD) and micro-Raman spectroscopy. In order to discriminate among diverse concomitant aging pathways potentially occurring upon working conditions, the effects of different stress factors were investigated: light and temperature. Evidence is gained of an essential structural stability, although an increased roughness at the ZnO/PM6:Y6 interface is deduced by EDXR measurements. On the contrary, an overall stability of the system subjected to thermal stress in the dark was observed, which is a clear indication of the photo-induced origin of the observed degradation phenomenon. Micro-Raman spectroscopy brings light on the origin of such effect, evidencing a photo-oxidation process of the active material in the device, using hygroscopic organic HTL, during continuous illumination in ambient moisture conditions. The process may be also triggered by a photocatalytic role of the ZnO layer. Therefore, an alternative configuration is proposed, where the hygroscopic HTL-X is replaced by the inorganic compound MoOx. The results show that such alternative configuration is stable under light stress (solar simulator), suggesting that the use of Molybdenum Oxide, limiting the photo-oxidation of the bulk PM6:Y6 active material, can prevent the cell from degradation.

On the Elusive Crystallography of Lithium-Rich Layered Oxides: Novel Structural Models.

Lithium-rich layered oxides (LRLOs) are one of the most attractive families among future positive electrode materials for the so-called fourth generation of lithium-ion batteries (LIBs). Their electrochemical performance is enabled by the unique ambiguous crystal structure that is still not well understood despite decades of research. In the literature, a clear structural model able to describe their crystallographic features is missing thereby hindering a clear rationalization of the interplay between synthesis, structure, and functional properties. Here, the structure of a specific LRLO, Li1.28 Mn0.54 Ni0.13 Co0.02 Al0.03 O2 , using synchrotron X-ray diffraction (XRD), neutron diffraction (ND), and High-Resolution Transmission Electron Microscopy (HR-TEM), is analyzed. A systematic approach is applied to model diffraction patterns of Li1.28 Mn0.54 Ni0.13 Co0.02 Al0.03 O2 by using the Rietveld refinement method considering the R 3 ¯ $\bar{3}$ m and C2/m unit cells as the prototype structures. Here, the relative ability of a variety of structural models is compared to match the experimental diffraction pattern evaluating the impact of defects and supercells derived from the R 3 ¯ $\bar{3}$ m structure. To summarize, two possible models able to reconcile the description of experimental data are proposed here for the structure of Li1.28 Mn0.54 Ni0.13 Co0.02 Al0.03 O2 : namely a monoclinic C2/m defective lattice (prototype Li2 MnO3 ) and a monoclinic defective supercell derived from the rhombohedral R 3 ¯ $\bar{3}$ m unit cell (prototype LiCoO2 ).

Insights into the LiI Redox Mediation in Aprotic Li-O2 Batteries: Solvation Effects and Singlet Oxygen Evolution.

Lithium-oxygen aprotic batteries (aLOBs) are highly promising next-generation secondary batteries due to their high theoretical energy density. However, the practical implementation of these batteries is hindered by parasitic reactions that negatively impact their reversibility and cycle life. One of the challenges lies in the oxidation of Li2O2, which requires large overpotentials if not catalyzed. To address this issue, redox mediators (RMs) have been proposed to reduce the oxygen evolution reaction (OER) overpotentials. In this study, we focus on a lithium iodide RM and investigate its role on the degradation chemistry and the release of singlet oxygen in aLOBs, in different solvent environments. Specifically, we compare the impact of a polar solvent, dimethyl sulfoxide (DMSO), and a low polarity solvent, tetraglyme (G4). We demonstrate a strong interplay between solvation, degradation, and redox mediation in OER by LiI in aLOBs. The results show that LiI in DMSO-based electrolytes leads to extensive degradation and to 1O2 release, affecting the cell performance, while in G4-based electrolytes, the release of 1O2 appears to be suppressed, resulting in better cyclability.

A Computational Study on Halogen/Halide Redox Mediators and Their Role in 1O2 Release in Aprotic Li-O2 Batteries.

We present a computational study on the redox reactions of small clusters of Li superoxide and peroxide in the presence of halogen/halide redox mediators. The study is based on DFT calculations with a double hybrid functional and an implicit solvent model. It shows that iodine is less effective than bromine in the oxidation of Li2O2 to oxygen. On the basis of our thermodynamic data, in solvents with a low dielectric constant, iodine does not spontaneously promote either the oxidation of Li2O2 or the release of singlet oxygen, while bromine could spontaneously trigger both events. When a solvent with a large dielectric constant is used, both halogens appear to be able, at least on the basis of thermodynamics, to react spontaneously with the oxides, and the ensuing reaction sequence turned out to be strongly exoergic, thereby providing a route for the release of significant amounts of singlet oxygen. The role of spin-orbit coupling in providing a mechanism for singlet-triplet intersystem crossing has also been assessed.

Smartphone-Based Electrochemical Biosensor for On-Site Nutritional Quality Assessment of Coffee Blends.

This work aimed to develop an easy-to-use smartphone-based electrochemical biosensor to quickly assess a coffee blend's total polyphenols (Phs) content at the industrial and individual levels. The device is based on a commercial carbon-based screen-printed electrode (SPE) modified with multi-walled carbon nanotubes (CNTs) and gold nanoparticles (GNPs). At the same time, the biological recognition element, Laccase from Trametes versicolor, TvLac, was immobilized on the sensor surface by using glutaraldehyde (GA) as a cross-linking agent. The platform was electrochemically characterized to ascertain the influence of the SPE surface modification on its performance. The working electrode (WE) surface morphology characterization was obtained by scanning electron microscopy (SEM) and Fourier-transform infrared (FT-IR) imaging. All the measurements were carried out with a micro-potentiostat, the Sensit Smart by PalmSens, connected to a smartphone. The developed biosensor provided a sensitivity of 0.12 µA/µM, a linear response ranging from 5 to 70 µM, and a lower detection limit (LOD) of 2.99 µM. Afterward, the biosensor was tested for quantifying the total Phs content in coffee blends, evaluating the influence of both the variety and the roasting degree. The smartphone-based electrochemical biosensor's performance was validated through the Folin-Ciocâlteu standard method.

Outstanding Compatibility of Hard-Carbon Anodes for Sodium-Ion Batteries in Ionic Liquid Electrolytes.

Hard carbons (HC) from natural biowaste have been investigated as anodes for sodium-ion batteries in electrolytes based on 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide ([EMI][FSI]) and N-trimethyl-N-butylammonium bis(fluorosulfonyl)imide ([N1114][FSI]) ionic liquids. The Na+ intercalation process has been analyzed by cyclic voltammetry tests, performed at different scan rates for hundreds of cycles, in combination with impedance spectroscopy measurements to decouple bulk and interfacial resistances of the cells. The Na+ diffusion coefficient in the HC host has been also evaluated via the Randles-Sevcik equation. Battery performance of HC anodes in the ionic liquid electrolytes has been evaluated in galvanostatic charge/discharge cycles at room temperature. The evolution of the SEI (solid electrochemical interface) layer grown on the HC surface has been carried out by Raman spectroscopy. Overall the sodiation process of the HC host is highly reversible and reproducible. In particular, a capacity retention exceeding 98 % of the initial value has been recorded in[N1114][FSI] electrolytes after more than 1500 cycles with a coulombic efficiency above 99 %, largely beyond standard carbonate-based electrolytes. Raman, transport properties and impedance confirms that ILs disclose the formation of SEI layers with superior ability to support the reversible Na+ intercalation with the possible minor contributions from the EMI+cation.

Some Considerations about the Anodic Limit of Ionic Liquids Obtained by Means of DFT Calculations.

Ionic liquids are good candidates as the main component of safe electrolytes for high-energy lithium-ion batteries. The identification of a reliable algorithm to estimate the electrochemical stability of ionic liquids can greatly speed up the discovery of suitable anions able to sustain high potentials. In this work, we critically assess the linear dependence of the anodic limit from the HOMO level of 27 anions, whose performances have been experimentally investigated in the previous literature. A limited r Pearson's value of ≈0.7 is found even with the most computationally demanding DFT functionals. A different model considering vertical transitions in a vacuum between the charged state and the neutral molecule is also exploited. In this case, the best-performing functional (M08-HX) provides a Mean Squared Error (MSE) of 1.61 V2 on the 27 anions here considered. The ions which give the largest deviations are those with a large value of the solvation energy, and therefore, an empirical model that linearly combines the anodic limit calculated by vertical transitions in a vacuum and in a medium with a weight dependent on the solvation energy is proposed for the first time. This empirical method can decrease the MSE to 1.29 V2 but still provides an r Pearson's value of ≈0.72.

Aprotic Sulfur-Metal Batteries: Lithium and Beyond.

Metal-sulfur batteries constitute an extraordinary research playground that ranges from fundamental science to applied technologies. However, besides the widely explored Li-S system, a remarkable lack of understanding hinders advancements and performance in all other metal-sulfur systems. In fact, similarities and differences make all generalizations highly inconsistent, thus unavoidably suggesting the need for extensive research explorations for each formulation. Here we review critically the most remarkable open challenges that still hinder the full development of metal-S battery formulations, starting from the lithium benchmark and addressing Na, K, Mg, and Ca metal systems. Our aim is to draw an updated picture of the recent efforts in the field and to shed light on the most promising innovation paths that can pave the way to breakthroughs in the fundamental comprehension of these systems or in battery performance.

Cellulose Nanocrystals as Additives in Electrospun Biocompatible Separators for Aprotic Lithium-Ion Batteries.

This work concerns the study of electrospun scaffolds as separators for aprotic lithium-ion batteries (LIBs) composed of the amorphous poly-d,l-lactide (PDLLA), in solution concentrations of 8, 10, and 12 wt % and in different ratios with cellulose nanocrystals (CNCs). PDLLA has been studied for the first time as a separator, taking into account its amorphous character that could facilitate electrolyte incorporation into the polymer matrix and influence ionic conductivity, together with CNCs, for reducing the hydrophobicity of the scaffolds. The embedding of the nanocrystals in the scaffolds was confirmed by X-ray diffraction analysis and attenuated total reflectance Fourier transform infrared spectroscopy. The polymer combination influenced the nanofibrous morphology as evaluated by scanning electron microscopy and modulated the electrochemical behavior of the membranes that was investigated through linear sweep voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy tests. Among the studied categories, the P12 series displayed a nonhomogeneous electrolyte resistance and electrochemical stability, differently from P10, whose results suggested their application in LIBs with standard formulation, as confirmed by a preliminary performance test of the P10N6 formulation in a full Li-ion cell configuration.

Pushing Stoichiometries of Lithium-Rich Layered Oxides Beyond Their Limits.

Lithium-rich layered oxides (LRLOs) are opening unexplored frontiers for high-capacity/high-voltage positive electrodes in Li-ion batteries (LIBs) to meet the challenges of green and safe transportation as well as cheap and sustainable stationary energy storage from renewable sources. LRLOs exploit the extra lithiation provided by the Li1.2TM0.8O2 stoichiometries (TM = a blend of transition metals with a moderate cobalt content) achievable by a layered structure to disclose specific capacities beyond 200-250 mA h g-1 and working potentials in the 3.4-3.8 V range versus Li. Here, we demonstrate an innovative paradigm to extend the LRLO concept. We have balanced the substitution of cobalt in the transition-metal layer of the lattice with aluminum and lithium, pushing the composition of LRLO to unexplored stoichiometries, that is, Li1.2+x (Mn,Ni,Co,Al)0.8-x O2-δ. The fine tuning of the composition of the metal blend results in an optimized layered material, that is, Li1.28Mn0.54Ni0.13Co0.02Al0.03O2-δ, with outstanding electrochemical performance in full LIBs, improved environmental benignity, and reduced manufacturing costs compared to the state-of-the-art.

Laser Irradiation of a Bio-Waste Derived Carbon Unlocks Performance Enhancement in Secondary Lithium Batteries.

Pyrolyzed carbons from bio-waste sources are renewable nanomaterials for sustainable negative electrodes in Li- and Na-ion batteries. Here, carbon derived from a hazelnut shell has been obtained by hydrothermal processing of the bio-waste followed by thermal treatments and laser irradiation in liquid. A non-focused nanosecond pulsed laser source has been used to irradiate pyrolyzed carbon particles suspended in acetonitrile to modify the surface and morphology. Morphological, structural, and compositional changes have been investigated by microscopy, spectroscopy, and diffraction to compare the materials properties after thermal treatments as well as before and after the irradiation. Laser irradiation in acetonitrile induces remarkable alteration in the nanomorphology, increase in the surface area and nitrogen enrichment of the carbon surfaces. These materials alterations are beneficial for the electrochemical performance in lithium half cells as proved by galvanostatic cycling at room temperature.

Study of the Electronic Structure of Alkali Peroxides and Their Role in the Chemistry of Metal-Oxygen Batteries.

We use a multiconfigurational and correlated ab initio method to investigate the fundamental electronic properties of the peroxide MO2- (M = Li and Na) trimer to provide new insights into the rather complex chemistry of aprotic metal-O2 batteries. These electrochemical systems are largely based on the electronic properties of superoxide and peroxide of alkali metals. The two compounds differ by stoichiometry: the superoxide is characterized by a M+O2- formula, while the peroxide is characterized by [M+]2O22-. We show here that both the peroxide and superoxide states necessarily coexist in the MO2- trimer and that they correspond to their different electronic states. The energetic prevalence of either one or the other and the range of their coexistence over a subset of the MO2- nuclear configurations is calculated and described via a high-level multiconfigurational approach.

Reactions in non-aqueous alkali and alkaline-earth metal-oxygen batteries: a thermodynamic study.

Multivalent aprotic metal-oxygen batteries are a novel concept in the applied electrochemistry field. These systems are variants of the so-called Li-air batteries and up to present are in their research infancy. The superoxide disproportionation reaction is a crucial step for the operation of any metal-oxygen redox system using aprotic solvents: in the best scenario, disproportionation leads to peroxide formation while in the worse one it releases singlet molecular oxygen. In this work we address the fundamental thermodynamics of such reaction for alkali (Li, Na and K) and alkaline earth (Be, Mg and Ca) metal-O2 systems using multiconfigurational ab initio methods. Our aim is to draw a comprehensive description of the disproportionation reaction from superoxides to peroxides and to provide the thermodynamic likelihood of the pathways to singlet oxygen release.

Comparison of the Performances of Different Computational Methods to Calculate the Electrochemical Stability of Selected Ionic Liquids.

The electrochemical stability windows (ESW) of selected ionic liquids have been calculated by comparing different computational approaches previously suggested in the literature. The molecular systems under study are based on di-alkyl imidazolium and tetra-alkyl ammonium cations coupled with two different imide anions (namely, bis-fluorosulfonyl imide and bis-trifluoromethyl sulfonyl imide), for which an experimental investigation of the ESW is available. Thermodynamic oxidation and reduction potentials have here been estimated by different models based on calculations either on single ions or on ionic couples. Various Density Functional Theory (DFT) functionals (MP2, B3LYP, B3LYP including a polarizable medium and empirical dispersion forces) were exploited. Both vertical and adiabatic transitions between the starting states and the oxidized or reduced states were considered. The approach based on calculations on ionic couples is not able to reproduce the experimental data, whatever the used DFT functional. The best quantitative agreement is obtained by calculations on single ions when the MP2 functional in vacuum is considered and the transitions between differently charged states are vertical (purely electronic without the relaxation of the structure). The B3LYP functional underestimates the ESW. The inclusion of a polar medium excessively widens the ESW, while a large shrinkage of the ESW is obtained by adopting an adiabatic transition scheme instead of a vertical transition one.

Mechanism of mediated alkali peroxide oxidation and triplet versus singlet oxygen formation.

Aprotic alkali metal-O2 batteries face two major obstacles to their chemistry occurring efficiently, the insulating nature of the formed alkali superoxides/peroxides and parasitic reactions that are caused by the highly reactive singlet oxygen (1O2). Redox mediators are recognized to be key for improving rechargeability. However, it is unclear how they affect 1O2 formation, which hinders strategies for their improvement. Here we clarify the mechanism of mediated peroxide and superoxide oxidation and thus explain how redox mediators either enhance or suppress 1O2 formation. We show that charging commences with peroxide oxidation to a superoxide intermediate and that redox potentials above ~3.5 V versus Li/Li+ drive 1O2 evolution from superoxide oxidation, while disproportionation always generates some 1O2. We find that 1O2 suppression requires oxidation to be faster than the generation of 1O2 from disproportionation. Oxidation rates decrease with growing driving force following Marcus inverted-region behaviour, establishing a region of maximum rate.

Removal of diclofenac from aqueous solutions by adsorption on thermo-plasma expanded graphite.

The adsorption of diclofenac on thermo-plasma expanded graphite (a commercial product) from water solutions was investigated. The adsorbent material was characterized by SEM, TEM, BET, Raman and X-ray diffraction analyses. Typical diffractogram and Raman spectrum of graphitic material, dimension of 24.02 nm as crystallite dimension and a surface area of 47 m2 g-1 were obtained. The effect of pH on the adsorption capacity was evaluated in the range 1-7 and the adsorption mechanism was described by kinetic and isothermal studies. Pseudo-second order and Dubinin-Radushkevich models agreed with theoretical values of adsorption capacity (i.e. 400 and 433 mg g-1, respectively) and resulted to be the best fit for kinetics and isothermal experimental data. The thermodynamics of the process was evaluated by plotting the adsorption capacity/concentration ratio at the equilibrium as a function of different values of the multiplicative inverse of temperature. Moreover, the adsorbent regeneration was also investigated, comparing two different remediation techniques. Solvent washing performed with NaOH 0.2 M and thermo-treatment carried out by heating in an oven at 105 °C for 2 h and then at 200 °C for 4 h. The thermo-treatment was the best technique to regenerate the adsorbent, ensuring same performance after 4 cycles of use and regeneration.