71 research outputs found
Atomistic Conversion Reaction Mechanism of WO3 in Secondary Ion Batteries of Li, Na, and Ca
Intercalation and conversion are two fundamental chemical processes for battery materials in response to ion insertion. The interplay between these two chemical processes has never been directly seen and understood at atomic scale. Here, using inâ
situ HRTEM, we captured the atomistic conversion reaction processes during Li, Na, Ca insertion into a WO3 single crystal model electrode. An intercalation step prior to conversion is explicitly revealed at atomic scale for the first time for Li, Na, Ca. Nanoscale diffraction and abâ
initio molecular dynamic simulations revealed that after intercalation, the inserted ionâoxygen bond formation destabilizes the transitionâmetal framework which gradually shrinks, distorts and finally collapses to an amorphous W and MxO (M=Li, Na, Ca) composite structure. This study provides a full atomistic picture of the transition from intercalation to conversion, which is of essential importance for both secondary ion batteries and electrochromic devices.Das Wechselspiel zwischen Ioneninterkalation und Umwandlung des WO3âElektrodenmaterials wurde durch InâsituâTEM auf atomarer Ebene untersucht. Die Bildung von IonâSauerstoffâBindungen destabilisiert das WO3âGerĂŒst: Es schrumpft, wird verzerrt und fĂ€llt schlieĂlich zu einer amorphen Wâ und MxOâVerbundstruktur (M=Li, Na, Ca) zusammen.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134843/1/ange201601542_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134843/2/ange201601542.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134843/3/ange201601542-sup-0001-misc_information.pd
Atomistic Conversion Reaction Mechanism of WO3 in Secondary Ion Batteries of Li, Na, and Ca
Intercalation and conversion are two fundamental chemical processes for battery materials in response to ion insertion. The interplay between these two chemical processes has never been directly seen and understood at atomic scale. Here, using inâ
situ HRTEM, we captured the atomistic conversion reaction processes during Li, Na, Ca insertion into a WO3 single crystal model electrode. An intercalation step prior to conversion is explicitly revealed at atomic scale for the first time for Li, Na, Ca. Nanoscale diffraction and abâ
initio molecular dynamic simulations revealed that after intercalation, the inserted ionâoxygen bond formation destabilizes the transitionâmetal framework which gradually shrinks, distorts and finally collapses to an amorphous W and MxO (M=Li, Na, Ca) composite structure. This study provides a full atomistic picture of the transition from intercalation to conversion, which is of essential importance for both secondary ion batteries and electrochromic devices.The interplay between ion intercalation and WO3 battery electrode conversion was investigated at atomic scale by using inâ
situ HRTEM. The ionâoxygen bond formation destabilizes the WO3 framework which gradually shrinks, distorts and finally collapses to an amorphous W and MxO (M=Li, Na, Ca) composite structure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135051/1/anie201601542.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135051/2/anie201601542-sup-0001-misc_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135051/3/anie201601542_am.pd
Recommended from our members
Electroplating lithium transition metal oxides.
Materials synthesis often provides opportunities for innovation. We demonstrate a general low-temperature (260°C) molten salt electrodeposition approach to directly electroplate the important lithium-ion (Li-ion) battery cathode materials LiCoO2, LiMn2O4, and Al-doped LiCoO2. The crystallinities and electrochemical capacities of the electroplated oxides are comparable to those of the powders synthesized at much higher temperatures (700° to 1000°C). This new growth method significantly broadens the scope of battery form factors and functionalities, enabling a variety of highly desirable battery properties, including high energy, high power, and unprecedented electrode flexibility
The enormous repetitive Antarctic krill genome reveals environmental adaptations and population insights
Antarctic krill (Euphausia superba) is Earthâsmost abundant wild animal, and its enormous biomass is vital to
the Southern Ocean ecosystem. Here, we report a 48.01-Gb chromosome-level Antarctic krill genome, whose
large genome size appears to have resulted from inter-genic transposable element expansions. Our assembly
reveals the molecular architecture of the Antarctic krill circadian clock and uncovers expanded gene
families associated with molting and energy metabolism, providing insights into adaptations to the cold
and highly seasonal Antarctic environment. Population-level genome re-sequencing from four geographical
sites around the Antarctic continent reveals no clear population structure but highlights natural selection
associated with environmental variables. An apparent drastic reduction in krill population size 10 mya and
a subsequent rebound 100 thousand years ago coincides with climate change events. Our findings uncover
the genomic basis of Antarctic krill adaptations to the Southern Ocean and provide valuable resources for
future Antarctic research
Bio-inspired geotechnical engineering: Principles, current work, opportunities and challenges
publishedVersio
Bio-inspired geotechnical engineering: principles, current work, opportunities and challenges
A broad diversity of biological organisms and systems interact with soil in ways that facilitate their growth and survival. These interactions are made possible by strategies that enable organisms to accomplish functions that can be analogous to those required in geotechnical engineering systems. Examples include anchorage in soft and weak ground, penetration into hard and stiff subsurface materials and movement in loose sand. Since the biological strategies have been âvettedâ by the process of natural selection, and the functions they accomplish are governed by the same physical laws in both the natural and engineered environments, they represent a unique source of principles and design ideas for addressing geotechnical challenges. Prior to implementation as engineering solutions, however, the differences in spatial and temporal scales and material properties between the biological environment and engineered system must be addressed. Current bio-inspired geotechnics research is addressing topics such as soil excavation and penetration, soilâstructure interface shearing, load transfer between foundation and anchorage elements and soils, and mass and thermal transport, having gained inspiration from organisms such as worms, clams, ants, termites, fish, snakes and plant roots. This work highlights the potential benefits to both geotechnical engineering through new or improved solutions and biology through understanding of mechanisms as a result of cross-disciplinary interactions and collaborations
Real-time Observation of Sintering Process of Carbon Supported Platinum Nanoparticles in Oxygen and Water through Environment TEM
Millimeter-Wave Propagation Measurement and Modeling in Indoor Corridor and Stairwell at 26 and 38 GHz
Accurate propagation characteristics are essential for future indoor millimeter-wave (mmWave) small cell network planning. This paper presents propagation measurements at 26 GHz and 38 GHz which are important candidate bands for fifth generation mmWave communication. Measurements are conducted in an indoor corridor, as well as a stairwell whose mmWave channel is seldom investigated before. In these measurements, an omnidirectional biconical antenna is used as transmitter and a steerable directional horn antenna is used as receiver. The directional and omnidirectional path loss exponents, shadow factors, cross-polarization discrimination ratios and root-mean-square delay spreads are analyzed for both line-of-sight and non-line-of-sight scenarios in both co-polarization and cross-polarization, and these characteristics are compared for different frequencies and environments. It is found obvious depolarization phenomenon in non-line-of-sight scenario for higher frequency. Compared to the corridor, the stairwell has larger path loss exponents and root-mean-square delay spreads, and the depolarization is also more evident in stairwell. The results in this paper are beneficial to building efficient and robust indoor mmWave communication systems
Revealing the Dynamics of Platinum Nanoparticle Catalysts on Carbon in Oxygen and Water Using Environmental TEM
Deactivation
of supported metal nanoparticle catalysts, especially
under relevant gas conditions, is a critical challenge for many technological
applications, including heterogeneous catalysis, electrocatalysis,
and fuel cells. It has been commonly realized that deactivation of
catalysts stems from surface area loss due to particle coarsening;
however, the mechanism for this remains largely unclear. Herein, we
use aberration-corrected environmental transmission electron microscopy,
at an atomic level, to observe in situ the dynamics of Pt catalysts
under fuel cell relevant gas and temperature conditions. Particle
migration and coalescence is observed to be the dominant coarsening
process. In comparison with the case of H<sub>2</sub>O, O<sub>2</sub> promotes Pt nanoparticle migration on the carbon surface. Surprisingly,
coating Pt/carbon with a nanofilm of electrolyte (Nafion ionomer)
leads to a faster migration of Pt in H<sub>2</sub>O than in O<sub>2</sub>, a consequence of a Nafionâcarbon interface water
âlubricationâ effect. Atomically, the particle coalescence
features reorientation of particles toward lattice matching, a process
driven by orientation-dependent van der Waals forces. These results
provide direct observations of the dynamics of metal nanoparticles
at the critical surface/interface under relevant conditions and yield
significant insights into the multiphase interaction in related technological
processes
- âŠ