59 research outputs found
Current-induced transition from particle-by-particle to concurrent intercalation in phase-separating battery electrodes
Many battery electrodes contain ensembles of nanoparticles that phase-separate on (de)intercalation. In such electrodes, the fraction of actively intercalating particles directly impacts cycle life: a vanishing population concentrates the current in a small number of particles, leading to current hotspots. Reports of the active particle population in the phase-separating electrode ​lithium iron phosphate (​LiFePO4; ​LFP) vary widely, ranging from near 0% (particle-by-particle) to 100% (concurrent intercalation). Using synchrotron-based X-ray microscopy, we probed the individual state-of-charge for over 3,000 ​LFP particles. We observed that the active population depends strongly on the cycling current, exhibiting particle-by-particle-like behaviour at low rates and increasingly concurrent behaviour at high rates, consistent with our phase-field porous electrode simulations. Contrary to intuition, the current density, or current per active internal surface area, is nearly invariant with the global electrode cycling rate. Rather, the electrode accommodates higher current by increasing the active particle population. This behaviour results from thermodynamic transformation barriers in ​LFP, and such a phenomenon probably extends to other phase-separating battery materials. We propose that modifying the transformation barrier and exchange current density can increase the active population and thus the current homogeneity. This could introduce new paradigms to enhance the cycle life of phase-separating battery electrodes
Renal clearable catalytic gold nanoclusters for in vivo disease monitoring
Ultra-small gold nanoclusters (AuNCs) have emerged as agile probes for in vivo imaging, as they exhibit exceptional tumour accumulation and efficient renal clearance properties. However, their intrinsic catalytic activity, which can enable increased detection sensitivity, has yet to be explored for in vivo sensing. By exploiting the peroxidase-mimicking activity of AuNCs and the precise nanometer size filtration of the kidney, we designed multifunctional protease nanosensors that respond to disease microenvironments to produce a direct colorimetric urinary readout of disease state in less than 1 h. We monitored the catalytic activity of AuNCs in collected urine of a mouse model of colorectal cancer where tumour-bearing mice showed a 13-fold increase in colorimetric signal compared to healthy mice. Nanosensors were eliminated completely through hepatic and renal excretion within 4 weeks after injection with no evidence of toxicity. We envision that this modular approach will enable rapid detection of a diverse range of diseases by exploiting their specific enzymatic signatures
Effect of divergence angle of ejector nozzle on aerosolisation of powdered nanoparticles
Dependence of Beam Quality on Optical Intensity Asymmetry in In-Phase Coherently Coupled VCSEL Array
Dependence of beam quality on optical intensity asymmetry among elements in in-phase coherently coupled vertical cavity surface emitting lasers array is analyzed using the finite-difference time domain solutions software. The analysis results reveal that the coupling efficiency of in-phased array decreases and the divergence increases as the level of optical intensity asymmetry increases. Furthermore, an addressable separated-contact three-element triangular in-phased array is fabricated and measured to verify the analysis. The array exhibits a relatively high of coupling efficiency of 24% and a near-diffraction-limit divergence of 3.2\ub0 (1.12 times of the diffraction limit, D.L.) when the optical intensity of each element is adjusted to be uniform. By degrading the optical intensity symmetry, the coupling efficiency decreases to 17.07% and the divergence increases to 4.03\ub0 ( 1.37
7 D.L.). After that, a much larger 10
7 10 array exhibiting in-phase characteristics is produced and its beam quality and optical uniformity are measured and discussed. Analysis and experiment results demonstrate that symmetric optical intensity among elements is essential for in-phased array to achieve high beam quality. Employing separate contacts in the array is proved an effective way to obtain uniform optical intensity and achieve high beam quality
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Studying Long QT Syndrome Caused by NAA10 Genetic Variants Using Patient-Derived Induced Pluripotent Stem Cells
Transfer-free, lithography-free, and micrometer-precision patterning of CVD graphene on SiO2toward all-carbon electronics
A method of producing large area continuous graphene directly on SiO 2 by chemical vapor deposition is systematically developed. Cu thin film catalysts are sputtered onto the SiO 2 and pre-patterned. During graphene deposition, high temperature induces evaporation and balling of the Cu, and the graphene "lands onto" SiO 2 . Due to the high heating and growth rate, continuous graphene is largely completed before the Cu evaporation and balling. 60 nm is identified as the optimal thickness of the Cu for a successful graphene growth and μm-large feature size in the graphene. An all-carbon device is demonstrated based on this technique
Friability and crushing strength of micrometer-size diamond abrasives used in microgrinding of optical glass
Single-walled carbon nanotube film-silicon heterojunction radioisotope betavoltaic microbatteries
Beyond Constant Current: Origin of Pulse-Induced Activation in Phase-Transforming Battery Electrodes
Mechanistic
understanding of phase transformation dynamics during
battery charging and discharging is crucial toward rationally improving
intercalation electrodes. Most studies focus on constant-current conditions.
However, in real battery operation, such as in electric vehicles during
discharge, the current is rarely constant. In this work we study current
pulsing in LiXFePO4 (LFP),
a model and technologically important phase-transforming electrode.
A current-pulse activation effect has been observed in LFP, which
decreases the overpotential by up to ∼70% after a short, high-rate
pulse. This effect persists for hours or even days. Using scanning
transmission X-ray microscopy and operando X-ray
diffraction, we link this long-lived activation effect to a pulse-induced
electrode homogenization on both the intra- and interparticle length
scales, i.e., within and between particles. Many-particle phase-field
simulations explain how such pulse-induced homogeneity contributes
to the decreased electrode overpotential. Specifically, we correlate
the extent and duration of this activation to lithium surface diffusivity
and the magnitude of the current pulse. This work directly links the
transient electrode-level electrochemistry to the underlying phase
transformation and explains the critical effect of current pulses
on phase separation, with significant implication on both battery
round-trip efficiency and cycle life. More broadly, the mechanisms
revealed here likely extend to other phase-separating electrodes,
such as graphite
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