Anionic Redox Activity in a Newly Zn-Doped Sodium Layered Oxide P2-Na2/3 Mn1− y Zn y O2 (0 < y < 0.23)

The revival of the Na‐ion battery concept has prompted intense research activities toward new sustainable Na‐based insertion compounds and their implementation in full Na‐ion cells. Efforts are parted between Na‐based polyanionic and layered compounds. For the latter, there has been a specific focus on Na‐deficient layered phases that show cationic and anionic redox activity similar to a Na0.67Mn0.72Mg0.28O2 phase. Herein, a new alkali‐deficient P2‐Na2/3Mn7/9Zn2/9O2 phase using a more electronegative element (Zn) than Mg is reported. Like its Mg counterpart, this phase shows anionic redox activity and no O2 release despite evidence of cationic migration. Density functional theory (DFT) calculations show that it is the presence of an oxygen nonbonding state that triggers the anionic redox activity in this material. The phase delivers a reversible capacity of 200 mAh g−1 in Na‐half cells with such a value be reduced to 140 mAh g−1 in full Na‐ion cells which additionally shows capacity decay upon cycling. These findings establish Na‐deficient layered oxides as a promising platform to further explore the underlying science behind O2 release in insertion compounds based on anionic redox activity

Reaching the Energy Density Limit of Layered O3‐NaNi 0.5 Mn 0.5 O 2 Electrodes via Dual Cu and Ti Substitution

International audienc

Energy storage applications of CdMoO₄ microspheres

In this study, a one-step hydrothermal method was used to synthesize cadmium molybdenum oxide and revealed cationic cetyltrimethylammonium bromide surfactant effects on material preparation and energy storage characteristics. X-ray diffraction confirmed tetragonal-phase CdMoO4. Symmetric stretching modes of molybdenum oxide were confirmed from a Raman spectrum. A Fourier-transform infrared spectrum confirmed the presence of functional groups. Scanning electron microscopy images revealed a bunch of hierarchical microspheres of about 100–200 nm diameter. The specific capacitance achieved for CdMoO4, 0.1 M CTAB + CdMoO4, and 0.2 M CTAB + CdMoO4 were 200 F/g, 310 F/g, and 382 F/g, respectively, at 0.5 A/g. In addition, long-term cyclic stability for the best performing electrode (0.2 M CTAB + CdMoO4) material was investigated to explore cyclic performances of the supercapacitor. During the experiment, 86.01% capacity was retained after 5000 cycles at 5 A/g. The product activity is promising for high-efficiency supercapacitors due to the ease of production, environmentally friendly nature, and low cost of the synthesized material.This work was supported by RUSA, UGC-SAP, DST-FIST, DST-PURSE grants. The authors extend their appreciation to the Researchers supporting project number (RSP-2020/247) King Saud University, Riyadh, Saudi Arabia

Highly efficient perovskite solar cells with Ba(OH)2 interface modification of mesoporous TiO2 electron transport layer

Outstanding photovoltaic performances together with some advantageous fabrication methods are the driving forces for recent research in perovskite solar devices. Interfacial engineering greatly influences the overall performance of the organic–inorganic perovskite solar cell as it alters energy band alignment, carrier recombination, and charge extraction/transport. In this work, Ba(OH)2 was spun between the meso-TiO2 electron transport and organic–inorganic perovskite absorber layers to engineer the interface and enhance the photovoltaic performance. Ba(OH)2 modification shifted the conduction band of meso-TiO2 upward such that better alignment with perovskite energy level, reduced carrier recombination, enhanced optical absorption, and electron transportation were observed. These enhancements led to paramount power conversion efficiency (PCE) of 17.53% for optimum Ba(OH)2 concentration of 5 mg/mL spun on meso-TiO2 but poorer PCE of 16.08% for the devices without interfacial treatment. Through this study, we demonstrated the use of interface modification as a straightforward yet powerful approach to enhance performances of conventional perovskite solar cells.Ministry of Education (MOE)Accepted versionThe research is supported by an AcRF Tier1 Grant (MOE2017-T1-002-142) from the Singapore Ministry of Education. We would thank Prof. Subodh Mhaisalkar, Executive Director of Energy Research Institute @ NTU (ERI@N) for supporting this work

Heterostructured SmCoO₃/rGO composite for high-energy hybrid supercapacitors

A supercapacitor is an efficient energy storage system that acts as an excellent booster to deliver high power density required for batteries and fuel cells. Recently, composite material–based supercapacitors have attracted much more interest as promising greener and more capable candidates in energy-saving use. In this work, samarium cobalt oxide–decorated reduced graphene oxide (SmCoO₃/rGO) was prepared employing solvothermal route and used as reliable electrode material. The maximum specific capacity achieved was 30.80 mAh/g for 1 A/g of SmCoO₃/rGO nanocomposite with capacity retention of 86.95%@5A/g over 5000 charge discharge cycles. Better electrochemical performance of samarium and reduced graphene oxide nanostructures prevent the transfer of electrons through electrochemical active sites, creating electronic and structural diversity of electro active material. In addition, SmCoO₃/rGO/AC hybrid supercapacitor device that delivered good energy and power density of 52 W h/kg and 752 W/kg at 1 A/g was designed. 74.28% capacitive retention and 98.26% coulombic efficiency was maintained over 15,000 cycles.This work was supported by RUSA, UGC-SAP, DST-FIST, DST-PURSE grants. The authors extend their appreciation to the Researchers supporting project number (RSP-2020/247) King Saud University, Riyadh, Saudi Arabia

Electrochemical energy storage and conversion applications of CoSn(OH)₆ materials

Supercapacitors are a boon in today's modern world. The role of a supercapacitor is important in providing electrical energy in the most efficient way for the usefulness of the society. Herein, co-precipitation technique was adapted to prepare electrodes for energy storage and water-splitting purposes. Role of ammonia at different concentrations was deliberated. Better 269 and 364 F/g capacitance was attained for best electrode from cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) curves, respectively. The capacitive and diffusion contribution of all electrodes were estimated and found to be 91.88 and 8.12 for the best sample. A better diffusion contribution of the higher-concentration ammonia sample revealed a higher specific capacitance. In this study, 91.33% capacitive retention and 90.38% columbic efficiency were calculated after 5000 cycles of charge and discharge. Further electrochemical method like linear sweep voltammetry (LSV) and chronoamperometry (CA) was explored for water-splitting applications and 367 mA/g current density with 264 mV overpotential was achieved in the LSV plot. CA test was carried out for 10 h to reveal 189 mA/g current density and delivered 74% stability. Therefore, the present study describes different technique to extend electrochemical supercapacitor and water-splitting purposes.This work was supported by UGC-SAP, DST-FIST, DST-PURSE, MHRD-RUSA grants

Triggering Anionic Redox Activity in Li 3 NbS 4 Through Cationic Disordering or Substitution

International audienceExtensive utilization of Li-ion batteries for varieties of applications necessitates ceaseless improvements of electrode materials for achieving higher energy density. Towards this goal, Li-rich layered oxides exhibiting high capacity due to cumulated cationic and anionic redox activities are under study for nearly a decade. Still, several unanswered questions remain with respect to these Li-driven anionic redox reactions in terms of the activation process and long-term consequences upon cycling. Here, the Li-rich Li3NbS4 phase is focused, and synthesized as two different polymorphs, namely ordered and disordered phases. From analyses of their chemical and electrochemical properties, a crystal-electronic structure relationship is unraveled that triggers the anionic redox activity in these compounds. Moreover, through complementary theoretical calculations, the capability of cationic disorder to trigger anionic redox activity via the hybridization of cationic and non-bonding anionic energy levels is shown. This finding is further supported by the appearance of anionic redox activity by introducing the disorder through cationic substitution. Altogether, the insights derived can help in designing new anionic redox materials with optimum performances for practical applications

Improved photovoltaic performance of triple-cation mixed-halide perovskite solar cells with binary trivalent metals incorporated into the titanium dioxide electron transport layer

Among the next-generation photovoltaic technologies, perovskite solar cells have attracted significant attention and interest. In addition to the perovskite absorber component, the adjacent layers within the stack play decisive roles in the stability and overall power conversion efficiency (PCE) of a device. In this study, we demonstrated the use of a solution-processed aluminium indium (AlIn)-TiO2 compact layer as a highly effective electron transport layer (ETL) to achieve outstanding performance of perovskite solar cells; our results showed that the incorporation of AlIn into the TiO2 layer allowed better energy band alignment of the ETL-perovskite interface, improved the transparency, and enhanced the conductivity as compared to the case of pristine TiO2. Via co-doping these trivalent metals, an enhancement in voltage, current density, and even fill factor was observed. In addition, the results obtained from electrochemical impedance spectroscopy (EIS) revealed that the AlIn-TiO2-based device exhibited larger recombination resistance, which significantly benefited the performance of the devices. As a result, the optimized AlIn-TiO2 ETL device attained the surpassing PCE of 19% as compared to the pristine TiO2 solar device having the PCE of 16.67%.Ministry of Education (MOE)Accepted versionWe would like to acknowledge the financial support received from the Singapore Ministry of Education through AcRF Tier1 grant MOE2017-T1-002-142. We thank Prof. Subodh Mhaisalkar, Executive Director of Energy Research Institute@NTU (ERI@N) for supporting this work. The authors acknowledge the Facility for Analysis, Characterization, Testing and Simulation (FACTS), Nanyang Technological University, Singapore, for the use of XPS/UPS facilities

Preparation and characterization of a stable FeSO4F-based framework for alkali ion insertion electrodes

Polyanionic electrode materials offer an attractive combination of safety benefits and tunable redox potentials. Thus far, phosphate-based phases have drawn the most interest with a subsequent surge of activity focused on the newly discovered family of fluorosulfate phases. Here, we report the preparation of a new potassium-based fluorosulfate, KFeSO4F, which, with removal of K, leads to a new polymorph of FeSO4F crystallizing in the high-temperature structure of KTiOPO4. This new phase which contains large, empty channels, is capable of reversibly inserting 0.9 Li+ per unit formula and can accommodate a wide variety of alkali ions including Li+, Na+, or K+. This finding not only expands the rich crystal chemistry of the fluorosulfate family but further suggests that a similar strategy can apply to other K-based polyanionic compounds in view of stabilizing new attractive host structures for insertion reactions. © 2012 American Chemical Society