This study investigated the influence of variations in the mixing ratio of ethylene carbonate (EC) to ethyl methyl carbonate (EMC) on the composition and effectiveness of the solid electrolyte interphase (SEI) in lithium-metal batteries. The SEI is crucial for battery performance, as it prevents continuous electrolyte decomposition and inhibits the growth of lithium dendrites, which can cause internal short circuits leading to battery failure. Although the properties of the SEI largely depend on the electrolyte solvent, the influence of the EC:EMC ratio on SEI properties has not yet been elucidated. Through electrochemical testing, ionic conductivity measurements, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, the formation of Li₂CO₃, LiF, and organolithium compounds on lithium surfaces was systematically analyzed. This study demonstrated that the EC:EMC ratio significantly affected the SEI structure, primarily owing to the promotion of the formation of a denser SEI layer. Specifically, the ratios of 1:1 and 1:3 facilitated a uniform distribution and prevalence of Li₂CO₃ and LiF throughout the SEI, thereby affecting cell performance. Thus, precise control of the EC:EMC ratio is essential for enhancing the mechanical robustness and electrochemical stability of the SEI, thereby providing valuable insights into the factors that either enhance or impede effective SEI formation.

This study examined the role of fluoroethylene carbonate (FEC) in stabilizing the solid electrolyte interphase (SEI) and enhancing the electrochemical performance of SiOx-based composite negative electrodes in lithium-ion batteries. Two electrolyte systems were used: 1.0 mol dm⁻³ (M) LiPF₆ in a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) with 0.5 wt.% VC, and 1.0 M LiPF₆ in a mixture of EC and EMC with 1.0 wt.% VC and 10 wt.% FEC. These systems enabled the investigation of how FEC contributes to SEI stabilization and cycling stability. FEC promotes the formation of a LiF-rich SEI layer, which mitigates volume expansion and enhances capacity retention. Additionally, the accumulation of Li₂CO₃ and Li₂O in the SEI was found to increase interfacial resistance, as observed through electrochemical impedance spectroscopy (EIS). Among the SiOx contents tested (0%, 3%, and 7.8%), the 3% SiOx content exhibited the best balance between SiOx and carbon nanotubes, resulting in improved SEI formation and enhanced electrochemical performance. These results offer insights into the optimization of electrolyte formulations for long-term cycling stability in SiOx-based lithium-ion batteries.

This study explores the potential of titanium disulfide (TiS₂) as an active material for aqueous calcium-ion batteries (CIBs). We investigate the electrochemical redox reactions of calcium ions within TiS₂ and assess its suitability for use in aqueous CIBs. Additionally, we examine the impact of varying electrolyte concentrations, ranging from 1.0 to 8.0 mol dm⁻³, on TiS₂ electrode reactions. Our findings reveal that TiS₂ exhibits distinct charge–discharge behaviors in various aqueous calcium-ion electrolytes. Notably, at higher electrolyte concentrations, TiS₂ effectively suppresses the hydrogen generation reaction caused by water decomposition. In situ X-ray diffraction analysis confirms the intercalation of Ca²⁺ ions between the TiS₂ layers during charging, which is a groundbreaking discovery, signifying TiS₂’s applicability in aqueous CIBs. X-ray photoelectron spectroscopy analysis further supports the formation of a solid electrolyte interphase (SEI) on the TiS₂ electrode surface, contributing to the suppression of electrolyte decomposition reactions. Furthermore, we investigate the influence of anions in the electrolyte on charge–discharge behavior. Our findings suggest that the choice of anion coordinated with Ca²⁺ ions affects the SEI formation and cycling performance. Understanding the role of anions in SEI formation is crucial for optimizing aqueous CIBs. In conclusion, this research underscores TiS₂’s potential as an active material for aqueous calcium-ion batteries and emphasizes the importance of the electrolyte composition in influencing SEI formation and battery performance, contributing to sustainable and efficient energy storage technologies.

Lithium metal negative electrodes are pivotal for next-generation batteries because of their exceptionally high theoretical capacity and low redox potential. However, their commercialization is constrained by critical challenges, including dendrite formation, volumetric instability, and the fragility of the solid electrolyte interphase (SEI). In this context, this review highlights the transformative potential of ex situ surface treatments, which stabilize lithium metal electrodes before cell assembly. Key advancements include inorganic and polymer-based coatings that enhance SEI stability and mitigate dendrite growth, three-dimensional host architectures that manage volumetric changes and improve lithium diffusion, and liquid-phase chemical modifications that enable uniform lithium deposition. These strategies are critically evaluated for their scalability, environmental sustainability, and long-term stability, paying particular attention to cost, complexity, and ecological considerations. In addition, their potential contributions to the development of advanced battery technologies are discussed, providing insights into pathways toward enhanced commercial viability. By synthesizing cutting-edge research and identifying unresolved challenges, this review provides a comprehensive roadmap for advancing safer, more efficient, and more durable lithium metal batteries, thereby bridging the gap between laboratory research and commercial adoption.