Ganguli Babu

Li-S batteries still suffer from two of the major challenges: polysulfide shuttle and low inherent conductivity of sulfur. Here, we report a facile way to develop a bifunctional separator coated with fluorinated multiwalled carbon nanotubes. Mild fluorination does not affect the inherent graphitic structure of carbon nanotubes as shown by transmission electron microscopy. Fluorinated carbon nanotubes show an improved capacity retention by trapping/repelling lithium polysulfides at the cathode, while simultaneously acting as the “second current collector”. Moreover, reduced charge-transfer resistance and enhanced electrochemical performance at the cathode-separator interface result in a high gravimetric capacity of around 670 mAh g⁻¹ at 4C. Unique chemical interactions between fluorine and carbon at the separator and the polysulfides, studied using DFT calculations, establish a new direction of utilizing highly electronegative fluorine moieties and absorption-based porous carbons for mitigation of polysulfide shuttle in Li-S batteries.

A layer-by-layer fabrication technique for a stacked on-chip supercapacitor operable in a wide range of temperatures (−20 °C to 70 °C) is demonstrated, and the prepared devices show competing performances at room and high temperatures.

Buffer reactions can prevent changes induced by external causes. Here, we demonstrate the significant buffer role of a very small amount of Mn in a self-optimized cathode for an aqueous Zn-ion battery. Our operando X-ray characterization studies reveal that the dissolution of most of the Mn in MnV₂O₄ during the first charging cycle induces atomic re-arrangement to form a disordered vanadium oxide phase with 0.88 at% Mn. Interestingly, the residual Mn ions exhibit voluntary migration between tetrahedral and octahedral sites during Zn²⁺ de/intercalation. This Mn migration not only stabilizes the main structure of the vanadium-based electrode, but also modulates the Fermi surface of V 3d against excessive drift. As result, the optimized cathode delivers an excellent capacity of 610.2 mA h g⁻¹ at 0.2 A g⁻¹ and long-term cycling stability over 4000 cycles. This buffer contribution via tunable metal ions exhibits high potential for applications in long-life metal-ion batteries and related fields.

Lithium batteries that could be charged on exposure to sunlight will bring exciting new energy storage technologies. Here, we report a photorechargeable lithium battery employing nature-derived organic molecules as a photoactive and lithium storage electrode material. By absorbing sunlight of a desired frequency, lithiated tetrakislawsone electrodes generate electron–hole pairs. The holes oxidize the lithiated tetrakislawsone to tetrakislawsone while the generated electrons flow from the tetrakislawsone cathode to the Li metal anode. During electrochemical operation, the observed rise in charging current, specific capacity, and Coulombic efficiency under light irradiation in contrast to the absence of light indicates that the quinone-based organic electrode is acting as both photoactive and lithium storage material. Careful selection of electrode materials with optimal bandgap to absorb the intended frequency of sunlight and functional groups to accept Li-ions reversibly is a key to the progress of solar rechargeable batteries.

Alkali and alkaline earth metal-ion batteries are currently among the most efficient electrochemical energy storage devices. However, their stability and safety performance are greatly limited when used with volatile organic liquid electrolytes. A solid state polymer electrolyte is a prospective solution even though poor ionic conductivity at room temperature remains a bottleneck. Here we propose the mixing of two similar polymer matrices, poly(dimethyl siloxane) and poly(ethylene oxide), to address this challenge. The resulting electrolyte matrix is denser and significantly improves room-temperature ionic conductivity. Ab initio analyses of the reaction between the cations and the polymers show that oxygen sites act as entrapment sites for the cations and that ionic conduction likely occurs through hopping between adjacent oxygen sites. Molecular dynamics simulations of the dynamics of both polymers and the dynamics of the polymer mix show that the more frequent and more pronounced molecular vibrations of the polymer mix are likely responsible for reducing the time between two consecutive oxygen entrapments, thereby speeding up the conduction process. This hypothesis is experimentally validated by the practically useful ionic conductivity (σ ≈ 10⁻⁴ S cm⁻¹ at 25 °C) and the improved safety parameters exhibited by a transparent flexible multi-cation (Li⁺, Na⁺ and Mg²⁺) conducting solid channel made up of the above mixed polymer system.

Organic electrode materials for lithium-ion batteries provide an enticing solution to alleviate challenges of sustainability, costliness, and humanitarian impact associated with the sourcing and recycling of current inorganic-based technologies. However, recent research efforts have focused on curtailing the instability of readily soluble organic molecules in electrolytes, which results in rapid capacity fading and short cycling lifetimes. Quinones, such as the naturally occurring red dye purpurin, have previously displayed competitive electrochemical properties to commercial LIB cathodes derived from the coordination of Li ions via redox-active carbonyl and hydroxyl functional groups. In order to combat solubility obstacles, this study successfully appends purpurin to the widely available and inexpensive polymer: 4-chloromethyl polystyrene. The resulting purpurin functionalized polystyrene displays a stable capacity of 150 mAh g-1 at current density of 50 mA g-1 for over 60 cycles. To validate the performance of this material, in-depth Li-ion binding mechanisms are elucidated through a unique comparison of solution-state characterization of soluble analogues, solid-state NMR spectroscopy performed on the polymer, and supplemented by computational studies.

Graphite anode have shown commercial success for over two decades, since the start of their use in commercial Li‐ion batteries, due to their high practical specific capacity, conductivity, and low lithiation potential. Graphite is to a large extent thermodynamically unfavorable for sodium‐ion intercalation and thus limits advancement in Na‐ion batteries. In this work, a β‐phase arsenic‐phosphorus monolayer is studied, which has recently been predicted to have semiconducting behavior and to be dynamically stable. First‐principles calculations based on density functional theory are used to explore the role of β‐AsP monolayer as a negative electrode for Na‐ion batteries. Cohesive energy, phonon spectrum, and molecule dynamics simulations confirm the thermodynamic stability and the possibility of experimentally synthesizing this material. The Na‐ion adsorption‐energies are found to be high (>−1.2 eV) on both sides (As‐ and P‐side). The ultra‐fast energy barriers for Na (0.046/0.053 V) over both sides imply high diffusion of Na‐ions on the surfaces of β‐AsP. During the evaluation of Na‐ion anode performance, the fully sodiated state is found to be Na₂AsP, which yields a high theoretical‐specific capacity of 506.16 mAh g⁻¹ and low average sodiation potential of 0.43 V versus Na/Na+.

In this paper, the thermal conductivity behavior of synthetic and natural esters reinforced with 2D nanostructures—single hexagonal boron nitride (h-BN), single molybdenum disulfide (MoS₂), and hybrid h-BN/MOS₂—were studied and compared to each other. As a basis for the synthesis of nanofluids, three biodegradable insulating lubricants were used: FR3^TM and VG-100 were used as natural esters and MIDEL 7131 as a synthetic ester. Two-dimensional nanosheets of h-BN, MoS_2, and their hybrid nanofillers (50/50 ratio percent) were incorporated into matrix lubricants without surfactants or additives. Nanofluids were prepared at 0.01, 0.05, 0.10, 0.15, and 0.25 weight percent of filler fraction. The experimental results revealed improvements in thermal conductivity in the range of 20–32% at 323 K with the addition of 2D nanostructures, and a synergistic behavior was observed for the hybrid h-BN/MoS₂ nanostructures.