Green Synthesis and Thermal Encapsulation of Organic Cathode for Aqueous Zn Battery

Aqueous zinc batteries are increasingly gaining attention of the researchers in recent years because of their environmental and user friendliness as well as the economic benefits of the zinc metal. Herein we report a ferrocene based organic cathode synthesized by following green chemistry principle and stabilized by low temperature thermal encapsulation in multiwalled carbon nano tubes (MWCNTs) for stable electrochemical performance. Successful intercalation was confirmed by XRD, Raman, FTIR spectra, TEM-HAADF imaging. Without encapsulation, material exhibited initial capacity of 64.7 mAhg-1 which was drastically faded with time due to dissolution of active material. However, by low temperature thermal encapsulation, the capacity was remarkably improved to 71.3 mAhg-1 with 94% columbic efficiency and 91% capacity retention at a current density of 75mAg-1 in a 100 charge/discharge cycles. The stability of the electrode has been explained on the basis of a friendly host-guest interaction between CNTs and the organic molecules by π-π stacking, dipole-dipole and dipole induced dipole interactions with detailed electrochemical and spectroscopic characterization. From this study we conclude that the thermal intercalation in MWCNTs has been found to be excellent method to stabilize the electrode materials in battery application.

A Sustainable Process for the Recovery of Valuable Metals from Spent Lithium Ion Batteries by Deep Eutectic Solvents Leaching

The feasibility of using low-environmental-impact leaching media to recover valuable metals from lithium ion batteries (LIBs) has been evaluated. Several deep eutectic solvents (DES) were tested as leaching agents in the presence of different type of additives (i.e., H2O2). The optimization of Co recovery was carried out by investigating various operating conditions, such as reaction time, temperature, solid (black mass) to liquid (DES) ratio, additive type, and concentration. Leaching with final selected DES choline chloride (33%), lactic acid (53%), and citric acid (13%) at 55 °C achieved an extraction yield of more than 95% for the cobalt. The leaching mechanism likely begins with the dissolution of the active material in the black mass (BM) followed by chelation of Co(II) with the DES. The results obtained confirm that those leaching media are an eco-friendly alternative to the strong inorganic acids used nowadays.

Fullerene-Tetrabenzofluorene (C60-TBF) in Multivalent Photosensitisation for Enhanced ZnO-based Photo-catalysts: Mono vs. Hexakis Adduct

Photo-catalysts offer a simple catalytic method with widespread applications like degradation of polluting dyes, hydrogen generation from water, etc., in the presence of a photon source like sunlight. The development of a second-generation photo-catalyst in the form of a nanocomposite is an integral part of research to improve the practical usefulness and efficiency of the process. A systematic study using the active material with controlled functional groups is required to understand the process in detail as well as to develop efficient photocatalytic systems. In this paper, we report the design, synthesis, detailed physicochemical studies, and self-assembly of interesting materials where fullerenes have been functionalized with polycyclic, aromatic, conjugated, butterfly-shaped molecules like Tetrabenzofluorene (TBF) using a well-known click chemistry approach. Detailed analyses using spectroscopic, electrochemical, and microscopic or X-ray diffraction (single crystal) techniques were undertaken for a clear understanding of their photophysical or self-assembly behavior. The functionalized fullerene material was mainly used so that comparative results could be presented where two units (mono adduct) or twelve units (hexakis adduct) of TBF molecules were attached separately. These comparative studies were beneficial for unambiguous interpretation of results and drawing definitive conclusions regarding the energy transfer with cascade-type systems. Finally, those results were useful for the logical understanding of photo-catalytic experiments using those designer fullerene materials.

Fabrication of an Immobilized Polyelectrolite Complex (PEC) Membrane from Pectin-Chitosan and Chromoionophore ETH 5294 for pH-Based Fish Freshness Monitoring

Considering the significance of its demand around the world, the accurate determination of fish freshness with a simple and rapid procedure has become an interesting issue for the fishing industry. Hence, we aimed to fabricate a new optical pH sensor based on a polyelectrolyte (PEC) membrane of pectin–chitosan and the active material chromoionophore ETH 5294. A trial-and-error investigation of the polymer compositions revealed that the optimum ratio of pectin to chitosan was 3:7. With an optimum wavelength region (λ) at 610 nm, the constructed sensor was capable of stable responses after 5 min exposure to phosphate-buffered solution. Furthermore, the obtained sensor achieved optimum sensitivity when the PBS concentration was 0.1 M, while the relative standard deviation values ranged from 2.07 to 2.34%, suggesting good reproducibility. Further investigation revealed that the sensor experienced decreased absorbance of 16.67–18.68% after 25 days of storage. Employing the optimum conditions stated previously, the sensor was tested to monitor fish freshness in samples that were stored at 4 °C and ambient temperature. The results suggested that the newly fabricated optical sensor could measure pH changes on fish skin after 25 h storage at room temperature (pH 6.37, 8.91 and 11.02, respectively) and 4 °C (pH 6.8, 7.31 and 7.92, respectively).

Tuning of Composition and Morphology of LiFePO4 Cathode for Applications in All Solid-State Lithium Metal Batteries

All solid-state rechargeable lithium metal batteries (SS-LMBs) are gaining more and more importance because of their higher safety and higher energy densities in comparison to their liquid-based counterparts. In spite of this potential, their low discharge capacities and poor rate performances limit them to be used as state-of-the-art SS-LMBs. This arise due to the low intrinsic ionic and electronic transport pathways within the solid components in the cathode during the fast charge/discharge processes. Therefore, it is necessary to have a cathode with good electron conducting channels to increase the active material utilization without blocking the movement of lithium ions. Since SS-LMBs require a different morphology and composition of the cathode, we selected LiFePO4 (LFP) as a prototype and, we have systematically studied the influence of the cathode composition by varying the contents of active material LFP, conductive additives (super C65 conductive carbon black and conductive graphite), ion conducting components (PEO and LiTFSI) in order to elucidate the best ion as well as electron conduction morphology in the cathode. In addition, a comparative study on different cathode slurry preparation methods was made, wherein ball milling was found to reduce the particle size and increase the homogeneity of LFP which further aids fast Li ion transport throughout the electrode. The SEM analysis of the resulting calendered electrode shows the formation of non-porous and crack-free structures with the presence of conductive graphite throughout the electrode. As a result, the optimum LFP cathode composition with solid polymer nanocomposite electrolyte (SPNE) delivered higher initial discharge capacities of 114 mAh g-1 at 0.2C rate at 30 ᴼC and 141 mAh g-1 at 1C rate at 70 ᴼC. When the current rate was increased to 2C, the electrode still delivered high discharge capacity of 82 mAh g-1 even after 500 cycle, which indicates that the optimum cathode formulation is one of the important parameters in building high rate and long cycle performing SS-LMBs.

Fabrication of inverted organic solar cells on stainless steel substrate with electrodeposited and spin coated ZnO buffer layers

Polymer based organic solar cells (OSCs) are of tremendous interest as suitable candidates for producing clean and renewable energy in recent years. In this study, inverted OSCs on stainless steel (SS) substrate with zinc oxide (ZnO) as the electron selective transport layer (ESTL), are investigated, occupying bulk heterojunction blend of regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) as the active material and poly-(4,3-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the hole transport layer (HTL). The device structure is SS/ZnO/P3HT:PCBM/PEDOT:PSS/Au. ZnO films are prepared by spin coating and electrodeposition techniques, followed by annealing under ambient conditions. The insertion of ZnO layer between the SS substrate and active layer has improved short-circuit current (J sc), open-circuit voltage (V oc), fill factor (FF), and power conversion efficiency (PCE) compared to those of the reference cell without ZnO layer, achieving the highest efficiency of 0.66% for the device with spin coated ZnO from sol–gel technique. This enhancement can be attributed to the effective electron extraction and the increased crystallinity of ZnO after annealing treatments at higher temperatures as further confirmed by X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses.

Mechanical Degradation Behavior of Single Crystal LiNixMnyCozO2 Cathode in Li-ion Battery by Indentation Analysis

LiNixMnyCozO2 (NMC) is among the most promising cathode materials for commercial Li-ion batteries due to its high electrochemical performance. However, NMC composite cathode is still plagued with limited cyclic performance, which is influenced by its structural stability during the cycling process. The cathode, which comprises of the active material, polymeric binder, and porous conductive matrix, often exhibits large structural variation during the electrochemical cycling process. This inevitably increases the challenge of measuring the mechanical properties of the material. Even though single crystal NMC possesses better stability as compared to the polycrystalline NMC, the electrochemical performance degradation of single crystal NMC cathode remains relatively unexplored. Different sample preparation methods are compared systematically in accordance to the previous report, and a new method of sample preparation is proposed. Nanoindentation instrument is used to measure the elastic modulus and hardness of the single crystal NMC particles. The measured elastic modulus and hardness of NMC particles, under different electrochemical environments, are dependent on a large number of nanoindentation experiments and statistical analysis of the result obtained from the carefully prepared samples. The sample preparation method is the key factor that can significantly influence the nanoindentation experiment results of the NMC particles. This work shows that the mechanical properties of the single crystal NMC particles degrade significantly with number of electrochemical cycles. The decreasing elastic modulus with the number of electrochemical cycles can be fitted using a two-parameter logarithm model.

Developments on Perovskite Solar Cells (PSCs): A Critical Review

This review provides detailed information on perovskite solar cell device background and monitors stepwise scientific efforts applied to improve device performance with time. The work reviews previous studies and the latest developments in the perovskite crystal structure, electronic structure, device architecture, fabrication methods, and challenges. Advantages, such as easy bandgap tunability, low charge recombination rates, and low fabrication cost, are among the topics discussed. Some of the most important elements highlighted in this review are concerns regarding commercialization and prototyping. Perovskite solar cells are generally still lab-based devices suffering from drawbacks such as device intrinsic and extrinsic instabilities and rising environmental concerns due to the use of the toxic inorganic lead (Pb) element in the perovskite (ABX3) light-active material. Some interesting recommendations and possible future perspectives are well articulated.

Novel 3D grid porous Li4Ti5O12 thick electrodes fabricated by 3D printing for high performance lithium-ion batteries

Three-dimensional (3D) grid porous electrodes introduce vertically aligned pores as a convenient path for the transport of lithium-ions (Li-ions), thereby reducing the total transport distance of Li-ions and improving the reaction kinetics. Although there have been other studies focusing on 3D electrodes fabricated by 3D printing, there still exists a gap between electrode design and their electrochemical performance. In this study, we try to bridge this gap through a comprehensive investigation on the effects of various electrode parameters including the electrode porosity, active material particle diameter, electrode electronic conductivity, electrode thickness, line width, and pore size on the electrochemical performance. Both numerical simulations and experimental investigations are conducted to systematically examine these effects. 3D grid porous Li4Ti5O12 (LTO) thick electrodes are fabricated by low temperature direct writing technology and the electrodes with the thickness of 1085 µm and areal mass loading of 39.44 mg·cm−2 are obtained. The electrodes display impressive electrochemical performance with the areal capacity of 5.88 mAh·cm−[email protected] C, areal energy density of 28.95 J·cm−[email protected] C, and areal power density of 8.04 mW·cm−[email protected] C. This study can provide design guidelines for obtaining 3D grid porous electrodes with superior electrochemical performance.