Origin of Excellent Charge Storage Properties of Defective Tin Disulphide in Magnesium/Lithium-Ion Hybrid Batteries.

Lithium-ion batteries (LIBs) are excellent electrochemical energy sources, albeit with existing challenges, including high costs and safety concerns. Magnesium-ion batteries (MIBs) are one of the potential alternatives. However, the performance of MIBs is poor due to their sluggish solid-state Mg2+ diffusion kinetics and severe electrode polarizability. Rechargeable magnesium-ion/lithium-ion (Mg2+/Li+) hybrid batteries (MLHBs) with Mg2+ and Li+ as the charge carriers create a synergy between LIBs and MIBs with significantly improved charge transport kinetics and reliable safety features. However, MLHBs are yet to reach a reasonable electrochemical performance as expected. This work reports a composite electrode material with highly defective two-dimensional (2D) tin sulphide nanosheets (SnSx) encapsulated in three-dimensional (3D) holey graphene foams (HGF) (SnSx/HGF), which exhibits a specific capacity as high as 600 mAh g-1 at 50 mA g-1 and a compelling specific energy density of ~ 330 Wh kg-1. The excellent electrochemical performance surpasses previously reported hybrid battery systems based on intercalation-type cathode materials under comparable conditions. The role played by the defects in the SnSx/HGF composite is studied to understand the origin of the observed excellent electrochemical performance. It is found that it is closely related to the defect structure in SnSx, which offers percolation pathways for efficient ion transport and increased internal surface area assessable to the charge carriers. The defective sites also absorb structural stress caused by Mg2+ and Li+ insertion. This work is an important step towards realizing high-capacity cathode materials with fast charge transport kinetics for hybrid batteries.

Review on physical impedance models in modern battery research.

Electrochemical impedance spectroscopy (EIS) is a versatile tool to understand complex processes in batteries. This technique can investigate the effects of battery components like the electrode and electrolyte, electrochemical reactions, interfaces, and interphases forming in the electrochemical systems. The interpretation of the EIS data is typically made using models expressed in terms of the so-called electrical equivalent circuits (EECs) to fit the impedance spectra. Therefore, the EECs must unambiguously represent the electrochemistry of the system. EEC models with a physical significance are more relevant than the empirical ones with their inherent imperfect description of the ongoing processes. This review aims to present the readers with the importance of physical EEC modeling within the context of battery research. A general introduction to EIS and EEC models along with a brief description of the mathematical formalism is provided, followed by showcasing the importance of physical EEC models for EIS on selected examples from the research on traditional, aqueous, and newer all-solid-state battery systems.

Facile synthesis of carbon dot and residual carbon nanobeads: Implications for ion sensing, medicinal and biological applications.

Synthesis of carbon dots (Cdots) via chemical route involves disintegration of carbon materials into nano-domains, wherein, after extraction of Cdots, the remaining carbon material is discarded. The present work focuses on studying even the leftover carbon residue namely, carbon nanobeads (CNBs) as an equally important material for applications on par with that of carbon dot. It employs oxidative treatment of carbonised gum olibanum resin (GOR) to produce the carbons namely Cdots and CNBs (as the residue). The Cdots (~5-10nm) exhibit blue-green fluorescence with an optical absorption at ~300nm unlike the CNBs (40-50nm) which fail to exhibit fluorescence. The fluorescence behaviour exhibited by Cdots were utilized for heavy metal ion sensing of Pb2+, Hg2+ and Cd2+ ions in aqueous media. Interestingly, both Cdots and CNBs are biocompatible to normal cell lines but cytotoxic to cancer cell lines, observed during several in vitro experiments (cell viability assay, cell cycle assay, apoptosis assay, ROS determination assay, caspase-9 activity assay). Additionally, Cdots exhibit bright green fluorescence in B16F10 cells. The Cdots and CNB's demonstrate multifunctional activities (sensor, cellular imaging and cancer therapy) in biomedical applications.