Two-dimensional ZnS@N-doped carbon nanoplates for complete lithium ion batteries

Metal sulfides are attractive anode materials for lithium ion batteries due to the high specific capacities and better electrochemical kinetics comparing to their oxide counterparts. In this paper, novel monocrystalline wurtzite ZnS@N-doped carbon (ZnS@N-C) nanoplates, whose morphology and phase are different from the common ZnS particles with cubic phase, are successfully synthesized. The ZnS@N-C nanoplates exhibit good cycling stability with a high reversible specific capacity of 536.8 mAh∙g-1 after 500 cycles at a current density of 500 mA∙g-1, which is superior to the pure ZnS nanoplates, illustrating the obvious effect of the N-doped carbon coating for alleviating volume change of the ZnS nanoplates and enhancing the electronic conductivity during charge/discharge processes. Furthermore, it is revealed that the ZnS single crystals with wurtzite phase in the ZnS@N-C nanoplates are transformed to the polycrystalline cubic phase ZnS after charge/discharge processes. In particular, the ZnS@N-C nanoplates are combined with the commercial LiNi0.6Co0.2Mn0.2O2 cathode to fabricate a new type of LiNi0.6Co0.2Mn0.2O2/ZnS@N-C complete battery, which exhibits good cycling stability up to 120 cycles at 1C rate after the prelithiation treatment on the ZnS@N-C anode, highlighting the potential of the ZnS@N-C nanoplates as an anode material for lithium ion battery.

Effect of ZnO Nanomaterial and Red and Green Cabbage Dyes on the Performance of Dye-Sensitised Solar Cells

Visible light can be converted into electricity using dye sensitised solar cells (DSSCs), with their performance mainly based on the type of dye used as a sensitiser. Currently, dyes extracted from natural sources are highly preferred by researchers in this field. Natural dyes reduce the high cost of metal complex sensitisers and replace expensive processes of chemical synthesis with simple extraction processes. Natural dyes are environmentally friendly, abundant, easily extractable, and safe. Their application has become a promising development in DSSC technology. In this study, two natural dyes extracted from the plant leaves of green cabbage (GC) and red cabbage (RC) that were used as sensitisers. The performance characteristics of RC and GC extracts were investigated using both cyclic voltammetry and amperometry methods for solar cell detection. At an extraction temperature of 60 °C maintained for 8 h under optimum conditions, the measured values of maximum power (Pm), fill factor (FF), and efficiency (η) were 1.36 mW/cm2, 92.34%, and 0.161% for RC, and 0.349 mW/cm2, 44.19%, and 0.095% for GC, respectively. The RC and GC extracts exhibited excellent electrochemical performance with respect to current density potential and good cycling stability.

V2O5/Carbon Nanotube/Polypyrrole Based Freestanding Negative Electrodes for High-Performance Supercapacitors

In this study, the vanadium pentoxide (V2O5), functionalized carbon nanotubes (f-CNT), and polypyrrole (PPy) based composites films have been prepared through a facile synthesis method and their electrochemical performance were evaluated as freestanding negative electrodes of supercapacitor. A hydrous V2O5 gel prepared by treating V2O5 powder with H2O2 was mixed with f-CNT to obtain V2O5/f-CNT composite film. V2O5/f-CNT composite was then coated with PPy through vapor phase polymerization method. The PPy deposited on the V2O5/f-CNT prevented the dissolution of V2O5 and thus resulted in an improved the capacitance and cycle life stability for V2O5/f-CNT/PPy composite electrode. V2O5/f-CNT/PPy freestanding negative electrode exhibited a high areal capacitance value (1266 mF cm−2 at a current density of 1 mA cm−2) and good cycling stability (83.0% capacitance retention after 10,000 charge-discharge cycles). The superior performance of the V2O5/f-CNT/PPy composite electrode can be attributed to the synergy between f-CNT with high conductivity and V2O5 and PPy with high-energy densities. Thus, V2O5/f-CNT/PPy composite based electrode can effectively mitigate the drawbacks of the low specific capacitance of CNTs and the poor cycling life of V2O5.

Mn-N-C Nanostructure Derived from MnO2-x/PANI as Highly Performing Cathode Additive in Li-S Battery

Highly dispersed Mn metallic nanoparticles (15.87 nm on average) on a nitrogen-doped porous carbon matrix were prepared by thermal treatment of MnO2-x/polyaniline (PANI), which was derived from the in situ polymerization of aniline monomers initiated by γ-MnO2 nanosheets. Owing to the large surface area (1287 m2/g), abundant active sites, nitrogen dopants and highly dispersed Mn sites on graphitic carbon, an impressive specific capacity of 1319.4 mAh g−1 with an admirable rate performance was delivered in a Li-S battery. After 220 cycles at 1 C, 80.6% of the original capacity was retained, exhibiting a good cycling stability.

SnS2 Nanosheets with RGO Modification as High-Performance Anode Materials for Na-Ion and K-Ion Batteries

To date, the fabrication of advanced anode materials that can accommodate both Na+ and K+ storage is still very challenging. Herein, we developed a facile solvothermal and subsequent annealing process to synthesize SnS2/RGO composite, in which SnS2 nanosheets are bonded on RGO, and investigated their potential as anodes for Na+ and K+ storage. When used as an anode in SIBs, the as-prepared SnS2/RGO displays preeminent performance (581 mAh g−1 at 0.5 A g−1 after 80 cycles), which is a significant improvement compared with pure SnS2. More encouragingly, SnS2/RGO also exhibits good cycling stability (130 mAh g−1 at 0.3 A g−1 after 300 cycles) and excellent rate capability (520.8 mAh g−1 at 0.05 A g−1 and 281.4 mAh g−1 at 0.5 A g−1) when used as anode for PIBs. The well-engineered structure not only guarantees the fast electrode reaction kinetics, but also ensures superior pseudocapacitance contribution during repeated cycles, which has been proved by kinetic analysis.

Synthesis of Nickel Fumarate and Its Electrochemical Properties for Li-Ion Batteries

Metal–organic frameworks (MOFs) have found a potential application in various domains such as gas storage/separation, drug delivery, catalysis, etc. Recently, they have found considerable attention for energy storage applications such as Li- and Na-ion batteries. However, the development of MOFs is plagued by their limited energy density that arises from high molecular weight and low volumetric density. The choice of ligand plays a crucial role in determining the performance of the MOFs. Here, we report a nickel-based one-dimensional metal-organic framework, NiC4H2O4, built from bidentate fumarate ligands for anode application in Li-ion batteries. The material was obtained by a simple chimie douce precipitation method using nickel acetate and fumaric acid. Moreover, a composite material of the MOF with reduced graphene oxide (rGO) was prepared to enhance the lithium storage performance as the rGO can enhance the electronic conductivity. Electrochemical lithium storage in the framework and the effect of rGO on the performance have been investigated by cyclic voltammetry, galvanostatic charge–discharge measurements, and EIS studies. The pristine nickel formate encounters serious capacity fading while the rGO composite offers good cycling stability with high reversible capacities of over 800 mAh g−1.

Investigating the Cycling Stability of Fe2WO6 Pseudocapacitive Electrode Materials

The stability upon cycling of Fe2WO6 used as a negative electrode material for electrochemical capacitors was investigated. The material was synthesized using low temperature conditions for the first time (220 °C). The electrochemical study of Fe2WO6 in a 5 M LiNO3 aqueous electrolyte led to a specific and volumetric capacitance of 38 F g−1 and 240 F cm−3 when cycled at 2 mV·s−1, respectively, associated with a minor capacitance loss after 10,000 cycles. In order to investigate this very good cycling stability, both surface and bulk characterization techniques (such as Transmission Electron Microscopy, Mössbauer spectroscopy, and magnetization measurements) were used. Only a slight disordering of the Fe3+ cations was observed in the structure, explaining the good stability of the Fe2WO6 upon cycling. This study adds another pseudocapacitive material to the short list of compounds that exhibit such a behavior up to now.