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Li–S batteries are promising alternatives due to their proven increased gravimetric capacity compared to Li–ion batteries. However, their development is hindered by many technical issues, one of the most challenging being the dissolution and shuttle of polysulfide species, which causes irreversible loss of cathode material leading to rapid capacity fading. Among the possible strategies to mitigate this effect, the choice of suitable solvents is easy to implement and has large room for improvement. To guide this quest, computationally-aided optimization is a powerful tool, provided that suitable descriptors are used to screen possible solvents. In this work, molecular dynamics simulations were performed for a typical lithium polysulfide Li2S6 dissolved in different solvents. Diffusion coefficients and their related activation energies were calculated, and thermodynamic properties like solvation energies and entropies were also evaluated. Additionally, a theoretical framework for computing the relative solubilities of lithium polysulfide is provided. For the set of solvents considered, we found that the system's viscosity appears as an important descriptor to correlate with different system properties. The donor number of the solvent also appears as a valid descriptor, for low-viscosity solvents. In general, it was found that higher viscosity solvents lead to lower diffusion rates and higher polysulfide solubility. These results suggest that the optimal choice to reduce the shuttle is a trade-off between high-viscosity solvents to reduce polysulfide diffusion and low-viscosity solvents to reduce its solubility, which could be further improved by properly tuning the donor number. [ABSTRACT FROM AUTHOR]

The study presents a hybrid hard-carbon/nanocrystalline-Bi2S3 material applicable for negative electrodes in sodium-ion batteries. Through a series of comprehensive analyzes, including electrochemical measurements, operando XRD, ex situ solid-state NMR, and high-resolution STEM imaging, the effectiveness of the HC/Bi2S3 hybrid configuration in the negative electrode function is elucidated with a focus on the underlying charge storage mechanism. Electrochemical analysis demonstrates the improved performance of the hybrid materials over the pristine HC negative electrode and highlights the robustness and stability of the HC/Bi2S3 hybrids over prolonged cycling even under high current densities. Here, the final capacities observed after 100 cycles reached a value of 252 mA h g−1, compared to 216 mA h g−1 of pristine HC. Cyclic voltammetry measurements demonstrate a complex charge storage behavior that integrates both surface and diffusion-driven processes at different potentials during reduction and oxidation. A series of phase transformations during cycling observed in operando XRD expose irreversible reactions during the initial cycle between Bi2S3 and sodium ions, such as the breakdown of the Bi2S3 nanocrystal structure. This phenomenon is further confirmed by the detection of Na2S species using ex situ solid-state NMR. High-resolution STEM imaging reveals morphological changes in Bi2S3 nanocrystals and highlights their resistance to pulverization due to their nanoscale dimensions. This work provides comprehensive insights into the electrochemical performance of the HC/Bi2S3 and sheds light on specific mechanisms and reactions occurring during cycling. [ABSTRACT FROM AUTHOR]

One of the possible solutions to circumvent the sluggish kinetics, low capacity, and poor integrity of inorganic cathodes commonly used in rechargeable aluminium batteries (RABs) is the use of redox-active polymers as cathodes. They are not only sustainable materials characterised by their structure tunability, but also exhibit a unique ion coordination redox mechanism that makes them versatile ion hosts suitable for voluminous aluminium cation complexes, as demonstrated by the poly(quinoyl) family. Recently, phenazine-based compounds have been found to have high capacity, reversibility and fast redox kinetics in aqueous electrolytes because of the presence of a C＝N double bond. Here, we present one of the first examples of a phenazine-based hybrid microporous polymer, referred to as IEP-27-SR, utilized as an organic cathode in an aluminium battery with an AlCl3/EMIMCl ionic liquid electrolyte. The preliminary redox and charge storage mechanism of IEP-27-SR was confirmed by ex situ ATR-IR and EDS analyses. The introduction of phenazine active units in a robust microporous framework resulted in a remarkable rate capability (specific capacity of 116 mA h g−1 at 0.5C with 77% capacity retention at 10C) and notable cycling stability, maintaining 75% of its initial capacity after 3440 charge–discharge cycles at 1C (127 days of continuous cycling). This superior performance compared to reported Al//n-type organic cathode RABs is attributed to the stable 3D porous microstructure and the presence of micro/mesoporosity in IEP-27-SR, which facilitates electrolyte permeability and improves kinetics. [ABSTRACT FROM AUTHOR]

Enhancing the performance of electrolytes stands as one of the key challenges for moving toward practical applications of Mg batteries. Within this work, we investigate different synthesis procedures for the state-of-the-art MgAlhfip electrolyte. The results show that the purity and electrochemical performance of MgAlhfip electrolytes depend on whether they are synthesized from organometallic or inorganic reagents. Additionally, electrolyte properties vary depending on the electrolyte preparation method, either in situ electrolyte formation or salt isolation. To improve electrolyte performance, we explore two approaches: additional salt isolation steps and the use of a scavenging additive. Salt precipitation results in a modest improvement in the coulombic efficiency of Mg plating/stripping, while a scavenging additive significantly reduces overpotentials and enhances coulombic efficiency, especially in electrolytes synthesized from inorganic reagents. Finally, investigated syntheses are evaluated in terms of their practical applicability through procedure complexity and costs of used chemicals. Based on this, we propose a synthesis procedure that strikes a balance between the electrochemical performance of Mg electrolyte and its costs. [ABSTRACT FROM AUTHOR]

Aluminum rechargeable batteries are seen as a next-generation battery technology based on abundant materials. However, the current standard Al electrolytes are based on expensive ionic liquids. In this paper, the potential use of three AlCl 3 /amide-based electrolytes is investigated as a low-cost alternative from the perspective of Al metal anode and organic cathode compatibility. Our investigation shows the promising electrochemical performance of amide electrolytes and specific differences between the electrolytes depending on amide alkyl chain length. In particular, amides with longer alkyl chains show better plating/stripping efficiency and lower overpotential compared to the shorter acetamide one. Similarly, organic cathode capacity retention is the best for the electrolyte with the longest alkyl chain. However, the cathode capacity retention is subpar to the standard ionic liquid-based Al electrolyte although it undergoes the same electrochemical mechanism of carbonyl bond reduction. Interestingly, there is no deterioration of the anthraquinone redox peak through the appearance of a side peak at a lower potential in amide-based electrolytes, which is observed in standard electrolyte based on ionic liquid. Amide-based electrolyte display promise for practical applicability, however, the low oxidation stability of amide-based electrolytes is identified as one of their key limitation and should be addressed in future work. • Different alkylamide-based Al electrolytes are investigated as cost-effective alternatives. • Amide-based Al electrolytes enable high Al metal plating/stripping efficiency. • Good capacity utilization and improved compatibility with organic cathodes. • Increased length of amide alkyl chain leads to improved electrochemical performance. • Identified a drawback of limited oxidative stability amide-based electrolytes. [ABSTRACT FROM AUTHOR]

Hard carbons are the most extended anode materials for sodium-ion batteries (SIBs); however, they suffer from several limitations such as low stability, poor rate performance and low initial Coulombic efficiency (iCE). Herein, a simple, fast, and low-cost surface treatment at room temperature using short-chain organic molecules: 3-mercaptopropionic acid (MPA), 1,2-ethanedithiol (EDT) and oxalic acid (OxA) has been applied to a hard carbon (C1400). The carbons treated with sulfur containing molecules (MPA or EDT) exhibit higher capacity (12 % capacity enhancement after 100th cycles at C/10 and 18 % enhancement at 1C vs. C1400). The introduction of these ligands leads to improved micropore blockage, helping in the reversible insertion of Na ions. Moreover, ex-situ X-ray photoelectron spectroscopy (XPS) analyses demonstrate that thiol functional groups promote the formation of favorable NaF and Na 2 O-rich solid electrolyte interfaces (SEI) leading to and faster sodium diffusion in the plateau region. Additionally, MPA and EDT treatments have been applied to a soft carbon (Vulcan XC-72R) resulting in a substantial 30 % capacity improvement after 100 cycles at 1C. These results demonstrate the wide applicability of the method as a straightforward and efficient strategy for improving the electrochemical properties of carbon anodes used in SIBs. This study introduces an efficient and simple surface treatment with short chain ligands that blocks micropores, improves sodium diffusion, and increases capacity of carbons used as anodes in sodium-ion batteries. Ligands with thiol functional groups promote a NaF and Na 2 O-rich SEI, leading to anodes with improved capacity and stability. [Display omitted] • Hard carbons are the most extended anode materials for sodium-ion batteries (SIBs); however, they show some limitations. • A simple, fast, low-cost treatment with small molecules blocks micropores, improves Na diffusion and increases capacity. • Ex - situ XPS demonstrates that thiol functional groups promote the formation of a favorable solid electrolyte interface. • The treatment improves performance of soft carbons as well, demonstrating the wide applicability of the method. [ABSTRACT FROM AUTHOR]

The thermodynamically unstable interface between metallic lithium and electrolyte poses a major problem for the massive commercialization of Li-metal batteries. In this study, we propose the use of a multicomponent protective coating based on cellulose modified with dimethylthexylsilyl group (TDMSC), single-ion conducting polymer P(LiMTFSI), and LiNO 3 (TDMSC-P(LiMTFSI)-LiNO 3 , namely PTL). The coating shows its positive effect by increasing the Coulombic efficiency in Li || Cu cells from 95.9 and 98.6% for bare Li, to >99.3% for Li coated (Li@PTL), with 1 M LiFSI in FEC:DEC and 1 M LiFSI in DME electrolyte, respectively. Symmetrical Li || Li PTL-coated cells exhibit a much more prolonged and stable cycling with a slower increase in overpotential compared to bare Li cells. Li@PTL anodes enable improved cycling of Li@PTL/LFP cells compared to noncoated cells in liquid electrolytes. In this respect, inhibition of high surface area lithium growth is confirmed through postcycling scanning electron microscopy. Remarkably, dendrite-free galvanostatic cycling is demonstrated in laboratory-scale solid-state battery cells assembled with LFP composite cathode (catholyte configuration with PEO + LiTFSI as ionically conducting binder) and a cross-linked PEO-based solid polymer electrolyte. The PTL protective coating enables improved stability of Li metal batteries in combination with smooth transport of Li + at the electrode-electrolyte interface and homogeneous lithium coating, highlighting its promising prospects in enhancing the performance and safety of lithium metal batteries by properly tuning the synergy between the coating components.