Aluminum oxide coatings on Co-rich cathodes and interactions with organic electrolyte

Authors: M. D. Hashan C. Peiris, Michael Woodcox, Diana Liepinya, Robert Shephard, Hao Liu, Manuel Smeu

Published: June 10, 2025

Lithium-ion batteries (LIBs) have become essential in modern energy storage;
however, their performance is often limited by the stability and efficiency of
their components, particularly the cathode and electrolyte. Transition metal
layered oxide cathodes, a popular choice for lithium-ion batteries (LIBs),
suffer from several degradation mechanisms, including capacity fading,
reactions with the electrolyte, unstable cathode-electrolyte interfaces, and
lattice breakdown during cycling. In recent years, oxide coating, such as
alumina, has emerged as a promising strategy to enhance the durability of
cathodes by forming a protective layer that mitigates detrimental reactions and
improves the stability of the cathode electrolyte interphase (CEI). This study
employs ab initio molecular dynamics (AIMD) simulations to investigate the
chemical and mechanical behavior of LiCoO2 cathodes with and without aluminum
oxide coatings in contact with an organic electrolyte. We examine the
interactions between electrolyte molecules with both bare and coated cathode
surfaces, focusing on the decomposition of ethylene carbonate (EC) and dimethyl
carbonate (DMC), the formation of oxygen species, and solvation dynamics, and
evaluate the mechanical robustness of the cathode-coating interface using
calculations of axial strain and cleavage energy. Our findings reveal that
alumina coatings effectively reduce electrolyte degradation and stabilize the
cathode structure, particularly under high-charge states. The coating's
thickness and structural orientation are crucial in enhancing mechanical
strength and minimizing detrimental reactions at the cathode-electrolyte
interface. These insights contribute to the development of more durable LIBs by
optimizing the interface chemistry and mechanical properties, providing a
pathway toward higher energy densities and longer cycle life.

Visible Brillouin-quadratic microlaser in a high-Q thin-film lithium niobate microdisk

Authors: Xiaochao Luo, Chuntao Li, Xingzhao Huang, Jintian Lin, Renhong Gao, Yifei Yao, Yingnuo Qiu, Yixuan Yang, Lei Wang, Huakang Yu, Ya Cheng

Published: June 10, 2025

Narrow-linewidth lasers at short/visible wavelengths are crucial for quantum
and atomic applications, such as atomic clocks, quantum computing, atomic and
molecular spectroscopy, and quantum sensing. However, such lasers are often
only accessible in bulky tabletop systems and remain scarce in integrated
photonic platform. Here, we report an on-chip visible Brillouin-quadratic
microlaser in a 117-um-diameter thin-film lithium niobate (TFLN) microdisk via
dispersion engineering. Enabled by the ultra-high Q factor of 4.0X10(6) and
small mode volume, strong photon-phonon interaction and high second-order
nonlinearity of the TFLN microdisk, narrow-linewidth Stokes Brillouin lasing
(SBL) is demonstrated with 10.17 GHz Brillouin shift under a 1560-nm pump,
exhibiting a short-term narrow linewidth of 254 Hz and a low threshold of only
1.81 mW. Meanwhile, efficient second harmonic generation (SHG) of the SBL
signal is also observed at 780 nm, with a normalized conversion efficiency of
3.61%/mW, made possible by simultaneous phase matching fulfillments for both
narrow-linewidth SBL and its SHG. This demonstration of an integrated
ultra-narrow linewidth visible wavelength Brillouin-quadratic lasers opens new
avenues toward chip-scale quantum information processing and precise metrology.

Bridging Electrostatic Screening and Ion Transport in Lithium Salt-Doped Ionic Liquids

Authors: Hyungshick Park, Bong June Sung, Jeongmin Kim

Published: June 10, 2025

Alkali salt-doped ionic liquids are emerging as promising electrolyte systems
for energy applications, owing to their excellent interfacial stability. To
address their limited ionic conductivity, various strategies have been
proposed, including modifying the ion solvation environment and enhancing the
transport of selected ions (e.g., Li$^+$). Despite the pivotal role of
electrostatic interactions in determining key physicochemical properties, their
influence on ion transport in such systems has received relatively little
attention. In this work, we investigate the connection between ion transport
and electrostatic screening using atomistic molecular dynamics simulations of
1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide
([pyr$_{14}$][TFSI]) doped with lithium bis(trifluoromethanesulfonyl)imide
(LiTFSI) at molar fractions x$_{LiTFSI}$ $\le$ 0.3. We find that the
charge-charge and density-density correlation functions exhibit oscillatory
exponential decay, indicating that LiTFSI doped [pyr$_{14}$][TFSI] is a charge-
and mass-dense system. The electrostatic screening length decreases with
increasing LiTFSI concentration, whereas the decay length of the
density-density correlation functions remains nearly unchanged. Notably, we
find that the x$_{LiTFSI}$-sensitive screening length serves as a central
length scale for disentangling species-specific contributions of ion pairs to
collective ion transport upon LiTFSI doping. This framework provides a unifying
perspective on the interplay between structure and transport in ionic liquid
systems.

Tuning of altermagnetism by strain

Authors: M. Khodas, Sai Mu, I. I. Mazin, K. D. Belashchenko

Published: June 6, 2025

For all collinear altermagnets, we sort out piezomagnetic free-energy
invariants allowed in the nonrelativistic limit and relativistic piezomagnetic
invariants bilinear in the N\'eel vector $\mathbf{L}$ and magnetization
$\mathbf{M}$, which include strain-induced Dzyaloshinskii-Moriya interaction.
The symmetry-allowed responses are fully determined by the nonrelativistic spin
Laue group. In the nonrelativistic limit, two distinct mechanisms are
discussed: the band-filling mechanism, which exists in metals and is
illustrated using the simple two-dimensional Lieb lattice model, and the
temperature-dependent exchange-driven mechanism, which is illustrated using
first-principles calculations for transition-metal fluorides. The leading
second-order nonrelativistic term in the strain-induced magnetization is also
obtained for CrSb. Piezomagnetism due to the strain-induced
Dzyaloshinskii-Moriya interaction is calculated from first principles for
transition-metal fluorides, MnTe, and CrSb. Finally, we discuss triplet
superconducting correlations supported by altermagnets and protected by
inversion rather than time-reversal symmetry. We apply the nonrelativistic
classification of Cooper pairs to describe the interplay between strain and
superconductivity in the two-dimensional Lieb lattice and in bulk rutile
structures. We show that triplet superconductivity is, on average, unitary in
an unstrained altermagnet, but becomes non-unitary under piezomagnetically
active strain.

Meta-analysis of Life Cycle Assessments for Li-Ion Batteries Production Emissions

Authors: Maurizio Clemente, Prapti Maharjan, Mauro Salazar, Theo Hofman

Published: June 5, 2025

This paper investigates the environmental impact of Li-Ion batteries by
quantifying manufacturing-related emissions and analyzing how electricity mix
and production scale affect emission intensity. To this end, we conduct a
meta-analysis of life cycle assessments on lithium-ion batteries published over
the past two decades, categorizing them by year, battery chemistry, functional
unit, system boundaries, and electricity mix. We then carry out a
cradle-to-gate assessment for a nickel manganese cobalt 811 battery with a
silicon-coated graphite anode, analyzing how variations in the carbon intensity
of the electricity mix affect emissions, with case studies for China, South
Korea, and Sweden. Finally, we develop a set of regression models that link
annual battery production and the carbon intensity of China's electricity mix
to the average mass-specific emissions observed each year. The meta-analysis
shows a median global warming potential of 17.63 kg CO2-eq./kg of battery, with
a standard deviation of 7.34. Differences in electricity mix mainly influence
emissions from the energy-intensive cell production, particularly from cathode
material processing. We found that a multivariate linear regression using
production volume and the carbon intensity of the Chinese electricity mix as
predictors explains emissions with moderate accuracy. The environmental impact
of battery manufacturing can be reduced by using clean energy sources in
production processes. However, achieving substantial reductions requires clean
energy throughout the entire supply chain, as importing materials from regions
with carbon-intensive electricity mixes can undermine these efforts. Our
findings also highlight the emission-reducing effect of learning associated
with increased production scale, supporting the integration of learning effects
in future life cycle assessment models.

Laterally Excited Bulk Acoustic Wave (LBAW) X-Cut Lithium Niobate Resonators

Authors: Walter Gubinelli, Ryan Tetro, Pietro Simeoni, Luca Colombo, Matteo Rinaldi

Published: June 4, 2025

In this work, Laterally excited Bulk Acoustic Wave (LBAW) resonators on X-cut
Lithium Niobate (LiNbO3) and, for the first time their higher-order overtones
(LOBAW) are demonstrated by embedding interdigitated electrodes recessed into
the piezoelectric thin film, allowing to exploit both S0 and SH0 vibrational
modes. This recessed electrode architecture decouples the dispersion relation
from film thickness, enabling lithographic tuning of resonance frequency and
on-chip multi-frequency scaling on a single substrate, while concurrently
increasing static capacitance density (C0) and reducing ohmic losses (Rs). The
excited SH0 modes exhibits Figures of Merit (FoM) of 437 at 673 MHz for the
fundamental tone and 53 at 1.05 GHz for the overtone. The proposed architecture
holds large potential for future 5G/6G advanced radio frequency front-end
modules, enabling on-chip multi-frequency scaling and improved performance.

Electrically-induced resonance shifts of whispering gallery resonators made of barium magnesium fluoride

Authors: Alexander Mrokon, Heike Kraft, Dongsung Shin, Hiroki Tanaka, Simon J. Herr, Karsten Buse, Ingo Breunig

Published: June 4, 2025

Barium magnesium fluoride (BMF) is a ferroelectric crystal with a
transparency range far beyond the one of other optical materials. In
particular, its low loss in the deep ultraviolet makes this material an unique
candidate for frequency conversion in this spectral range. Due to its
relatively weak second-order nonlinearity, a resonant configuration such as an
optical whispering gallery would be beneficial. We show that femtosecond-laser
based material processing enables the reliable fabrication of BMF whispering
gallery resonators with quality factors beyond $10^7$. Their resonance
frequencies can be shifted linearly by applying electric fields between the
$+c$ and $-c$ faces of the crystal. The slope of the shift is
$-0.8$~MHz/(V/mm). It seems that the origin of this shift is piezoelectricity,
while the electro-optic effect is negligible. Our results pave the way for
millimeter-sized frequency converters in the deep ultraviolet. Furthermore,
they indicate that a careful determination of fundamental material properties
is still necessary.

Graphene Electro-Absorption Modulators for Energy-Efficient and High-Speed Optical Transceivers

Authors: M. Tiberi, A. Montanaro, C. Wen, J. Zhang, O. Balci, S. M. Shinde, S. Sharma, A. Meersha, H. Shekhar, J. E. Muench, B. R. Conran, K. B. K. Teo, M. Ebert, X. Yan, Y. Tran, M. Banakar, C. Littlejohns, G. T. Reed, M. Romagnoli, A. Ruocco, V. Sorianello, A. C. Ferrari

Published: June 3, 2025

The increasing demand for energy-efficient hardware for artificial
intelligence (AI) and data centres requires integrated photonic solutions
delivering optical transceivers with Tbit/s data rates and energy
consumption$<$1pJ/bit. Here, we report double single-layer graphene
electro-absorption modulators on Si optimized for energy-efficient and
ultra-fast operation, demonstrating 67GHz bandwidth and 80Gbit/s data rate, in
both O and C bands, using a fabrication tailored for wafer-scale integration.
We measure a data rate$\sim$1.6 times larger than previously reported for
graphene. We scale the modulator's active area down to 22$\mu$m$^2$, achieving
a dynamic power consumption$\sim$58fJ/bit, $\sim$3 times lower than previous
graphene modulators and Mach-Zehnder modulators based on Si or lithium niobate.
We show devices with$\sim$0.037dB/V$\mu$m modulation efficiency,$\sim$16 times
better than previous demonstrations based on graphene. This paves the way to
wafer-scale production of graphene modulators on Si useful for Tbit/s optical
transceivers and energy-efficient AI

Stringent Constraints on New Pseudoscalars from Precision Hyperfine Splitting Measurements

Authors: Cedric Quint, Fabian Heiße, Joerg Jaeckel, Lutz Leimenstoll, Christoph H. Keitel, Zoltán Harman

Published: June 3, 2025

Axion-like particles and similar new pseudoscalar bosons coupled to nucleons
and electrons are predicted to lead to spin-dependent forces in atoms and ions.
We argue that hyperfine structure measurements in the hydrogen- and
lithium-like charge states are a sensitive probe to this effect. Employing
specific differences of these splittings reduces uncertainties due to nuclear
effects in hyperfine structure calculations and measurements. Using this, we
show that existing measurements on Be provide competitive limits in the region
$m_{\phi}\gtrsim 100\,{\rm keV}$, improving upon existing constraints by up to
a factor of $8$. We also find that future measurements on Cs and In have a
further order of magnitude improved discovery potential when compared with
existing bounds.

A mesoscale phase-field model of intergranular liquid lithium corrosion of ferritic/martensitic steels

Authors: A. Lhoest, S. Kovacevic, D. Nguyen-Manh, J. Lim, E. Martínez-Pañeda, M. Wenman

Published: June 3, 2025

A phase-field model is developed to simulate intergranular corrosion of
ferritic/martensitic steels exposed to liquid lithium. The chromium
concentration of the material is used to track the mass transport within the
metal and liquid (corrosive) phase. The framework naturally captures
intergranular corrosion by enhancing the diffusion of chromium along grain
boundaries relative to the grain bulk with no special treatment for the
corrosion front evolution. The formulation applies to arbitrary 2D and 3D
polycrystalline geometries. The framework reproduces experimental measurements
of weight loss and corrosion depth for a 9 wt\% Cr ferritic/martensitic steel
exposed to static lithium at 600 $^\circ$C. A sensitivity analysis, varying
near-surface grain density, grain size, and chromium depletion thickness,
highlights the microstructural influence in the corrosion process. Moreover,
the significance of saturation is considered and evaluated. Simulation results
show that near-surface grain density is a deciding factor, whereas grain size
dictates the susceptibility to intergranular corrosion.