Energy storage mechanisms in vacancy-ordered Wadsley-Roth layered niobates

Wadsley–Roth (WR) crystallographic shear structures demonstrate high energy and power densities as Li-ion battery anode materials. We report the (de)lithiation behavior of two WR-derived layered niobates: NaNb_{3}O_{8} and KNb_{3}O_{8}. Both demonstrate multi-electron (Nb5+/Nb3+) redox on the first discharge, reacting with ≈5 mol Li per mol ANb_{3}O_{8}. Li intercalation in NaNb_{3}O_{8} is dominated by Li-diffusion kinetics and evolution of the interlayer structure, with Li initially filling octahedral sites near the interlayer space to draw the layers together to form a (2 × 2)_{∞} WR structure. This average structure change pushes Na ions into the square channels, blocking fast Li diffusion down the square channels that provide the fast Li-ion conduction in most WR materials. Upon charge, Li ions incorporated into the octahedral WR sites (ordered vacancies in the layered structure) are extracted, revealing a new, reversible Li site for additional capacity in WR-like materials. The behavior of KNb_{3}O_{8} is similar, but has additional hysteresis associated with its larger counter-cation. While neither layered niobate matches the demonstrated performance of WR materials, by studying them, we identify a route for increased capacity in WR-like frameworks. Additionally, we identify the important role of Li diffusion kinetics and counter-cations in the cycling behavior of WR-derived structures

Local Structure Evolution and Modes of Charge Storage in Secondary Li-FeS2_{2} Cells

In the pursuit of high-capacity electrochemical energy storage, a promising domain of research involves conversion reaction schemes, wherein electrode materials are fully transformed during charge and discharge. There are, however, numerous difficulties in realizing theoretical capacity and high rate capability in many conversion schemes. Here we employ operando studies to understand the conversion material FeS$_{2}$, focusing on the local structure evolution of this relatively reversible material. X-ray absorption spectroscopy, pair distribution function analysis, and first-principles calculations of intermediate structures shed light on the mechanism of charge storage in the Li-FeS$_{2}$ system, with some general principles emerging for charge storage in chalcogenide materials. Focusing on second and later charge/discharge cycles, we find small, disordered domains that locally resemble Fe and Li$_{2}$S at the end of the first discharge. Upon charge, this is converted to a Li-Fe-S composition whose local structure reveals tetrahedrally coordinated Fe. With continued charge, this ternary composition displays insertion-extraction behavior at higher potentials and lower Li content. The finding of hybrid modes of charge storage, rather than simple conversion, points to the important role of intermediates that appear to store charge by mechanisms that more closely resemble intercalation.M.M.B. acknowledges support by the Fletcher Jones and Peter J. Frenkel Foundation Fellowships. V.V.T.D.-N. is supported by the University of California President’s Postdoctoral Fellowship and the UCSB California NanoSystems Institute Elings Prize Fellowship. V.V.T.D.-N. gratefully acknowledges the Southern California Electrochemical Energy Storage Alliance (SCEESA), supported by the UCSB CNSI. Experiments at UCSB made use of MRL facilities, supported by the MRSEC Program of the NSF under Grant No. NSF-DMR 1121053. M.A.L. was supported by the RISE program through Grant No. NSF-DMR 1121053. This work was partially supported by the IMI Program of the National Science Foundation under Award No. DMR 08-43934. M.M. and A.J.M. acknowledge the support from the Winton Programme for the Physics of Sustainability. C.P.G. and S.B. thank EPSRC for financial support. This research made use of resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. X-ray absorption experiments were performed at APS 20-BM-B under GUP-41555. Sector 20 operations are supported by the U.S. DOE and the Canadian Light Source. X-ray scattering experiments were performed at APS 11-ID-B under GUP-42128 and GUP-45245

Trapped in the prison of the mind: notions of climate-induced (im)mobility decision-making and wellbeing from an urban informal settlement in Bangladesh

The concept of Trapped Populations has until date mainly referred to people ‘trapped’ in environmentally high-risk rural areas due to economic constraints. This article attempts to widen our understanding of the concept by investigating climate-induced socio-psychological immobility and its link to Internally Displaced People’s (IDPs) wellbeing in a slum of Dhaka. People migrated here due to environmental changes back on Bhola Island and named the settlement Bhola Slum after their home. In this way, many found themselves ‘immobile’ after having been mobile—unable to move back home, and unable to move to other parts of Dhaka, Bangladesh, or beyond. The analysis incorporates the emotional and psychosocial aspects of the diverse immobility states. Mind and emotion are vital to better understand people’s (im)mobility decision-making and wellbeing status. The study applies an innovative and interdisciplinary methodological approach combining Q-methodology and discourse analysis (DA). This mixed-method illustrates a replicable approach to capture the complex state of climate-induced (im)mobility and its interlinkages to people’s wellbeing. People reported facing non-economic losses due to the move, such as identity, honour, sense of belonging and mental health. These psychosocial processes helped explain why some people ended up ‘trapped’ or immobile. The psychosocial constraints paralysed them mentally, as well as geographically. More empirical evidence on how climate change influences people’s wellbeing and mental health will be important to provide us with insights in how to best support vulnerable people having faced climatic impacts, and build more sustainable climate policy frameworks

Microplasmas for direct, substrate-independent deposition of nanostructured metal oxides

A general, substrate-independent method for plasma deposition of nanostructured, crystalline metal oxides is presented. The technique uses a flow-through, micro-hollow cathode plasma discharge (supersonic microplasma jet) with a "remote" ring anode to deliver a highly directed flux of growth species to the substrate. A diverse range of nanostructured materials (e.g., CuO, alpha-Fe2O3, and NiO) can be deposited on any room temperature surface, e.g., conductors, insulators, plastics, fibers, and patterned surfaces, in a conformal fashion. The effects of deposition conditions, substrate type, and patterning on film morphology, nanostructure, and surface coverage are highlighted. The synthesis approach presented herein provides a general and tunable method to deposit a variety of functional and hierarchical metal oxide materials on many different surfaces. High surface area, conversion-type CuO electrodes for Li-ion batteries are demonstrated as a proof-of-concept example. Published by AIP Publishing