NASA’s IXPE Measures White Dwarf Star for First Time - UNIVERSE

This artist’s concept depicts a smaller white dwarf star pulling material from a larger star, right, into an accretion disk. Earlier this year, scientists used NASA’s IXPE (Imaging X-ray Polarization Explorer) to study a white dwarf star and its X-ray polarization.

MIT/Jose-Luis Olivares

By Michael Allen 
 
For the first time, scientists have used NASA’s IXPE (Imaging X-ray Polarization Explorer) to study a white dwarf star. Using IXPE’s unique X-ray polarization capability, astronomers examined a star called the intermediate polar EX Hydrae, unlocking the geometry of energetic binary systems. 
 
In 2024, IXPE spent nearly one week focused on EX Hydrae, a white dwarf star system located in the constellation Hydra, approximately 200 light-years from Earth. A paper about the results published in the Astrophysical Journal. Astrophysics research scientists based at the Massachusetts Institute of Technology in Cambridge led the study, along with co-authors at the University of Iowa, East Tennessee State University, University of Liége, and Embry Riddle Aeronautical University. 
 
A white dwarf star occurs after a star runs out of hydrogen fuel to fuse in its core but is not massive enough to explode as core-collapse supernovae. What remains is very dense, roughly the same diameter as Earth with as much mass as our Sun.  
 
EX Hydrae is in a binary system with a main sequence companion star, from which gas is continuously falling onto the white dwarf. How exactly the white dwarf is accumulating, or accreting, this matter and where it arrives on the white dwarf depends on the strength of the white dwarf star’s magnetic field. 
 
In the case of EX Hydrae, its magnetic field is not strong enough to focus matter completely at the star’s poles. But, it is still rapidly adding mass to the accretion disk, earning the classification “intermediate polars. 

In an intermediate polar system, material forms an accretion disk while also being pulled towards its magnetic poles. During this phenomenon, matter reaches tens of millions of degrees Fahrenheit, bouncing off other material bound to the white dwarf star, creating large columns of gas that emit high-energy X-rays – a cosmic situation perfect for IXPE to study.

“NASA IXPE’s one-of-a-kind polarimetry capability allowed us to measure the height of the accreting column from the white dwarf star to be almost 2,000 miles high – without as many assumptions required as past calculations,” said Sean Gunderson, MIT scientist and lead author on the paper. “The X-rays we observed likely scattered off the white dwarf’s surface itself. These features are far smaller than we could hope to image directly and clearly show the power of polarimetry to ‘see’ these sources in detail never before possible.”

Information from IXPE’s polarization data of EX Hydrae will help scientists understand other highly energetic binary systems.

More about IXPE 

The IXPE mission, which continues to provide unprecedented data enabling groundbreaking discoveries about celestial objects across the universe, is a joint NASA and Italian Space Agency mission with partners and science collaborators in 12 countries. It is led by NASA’s Marshall Space Flight Center in Huntsville, Alabama. BAE Systems, Inc., headquartered in Falls Church, Virginia, manages spacecraft operations together with the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder. Learn more about IXPE’s ongoing mission here: https://www.nasa.gov/ixpe 

Source: NASA’s IXPE Measures White Dwarf Star for First Time - NASA   

Ultrathin polymer layer extends lifespan of anode-free lithium metal batteries - Engineering - Energy & Green Tech

Schematic of an ultrathin artificial polymer layer (15 nm thick) introduced onto the electrode surface. Credit: Joule (2025). DOI: 10.1016/j.joule.2025.102226

Anode-free lithium metal batteries, which have attracted attention as candidates for electric vehicles, drones, and next-generation high-performance batteries, offer much higher energy density than conventional lithium-ion batteries. However, their short lifespan has made commercialization difficult.

KAIST researchers have now moved beyond conventional approaches that required repeatedly changing electrolytes and have succeeded in dramatically extending battery life through electrode surface design alone.

A research team led by Professors Jinwoo Lee and Sung Gap Im of the Department of Chemical and Biomolecular Engineering fundamentally resolved the issue of interfacial instability—the greatest weakness of anode-free lithium metal batteries—by introducing an ultrathin artificial polymer layer with a thickness of 15 nanometers (nm) on the electrode surface.

The results are published in Joule.

How anode-free batteries work

Anode-free lithium metal batteries have a simple structure that uses only a copper current collector instead of graphite or lithium metal at the anode. This design offers advantages such as 30–50% higher energy density compared to conventional lithium-ion batteries, lower manufacturing costs, and simplified processes.

Design rationale of the current collector-modifying artificial polymer layer and the SEI formation mechanism. Credit: Joule (2025). DOI: 10.1016/j.joule.2025.102226

However, during the initial charging process, lithium deposits directly onto the copper surface, rapidly consuming the electrolyte and forming an unstable solid electrolyte interphase (SEI), which leads to a sharp reduction in battery lifespan.

Rather than changing the electrolyte composition, the research team chose a strategy of redesigning the electrode surface where the problem originates.

By forming a uniform ultrathin polymer layer on the copper current collector using an iCVD (initiated chemical vapor deposition) process, they found that this layer regulates interactions with the electrolyte, precisely controlling lithium-ion transport and electrolyte decomposition pathways.

In conventional batteries, electrolyte solvents decompose to form soft and unstable organic SEI layers, causing non-uniform lithium deposition and promoting the growth of sharp, needle-like dendrites.

In contrast, the polymer layer developed in this study does not readily mix with the electrolyte solvent, inducing the decomposition of salt components rather than solvents.

As a result, a rigid and stable inorganic SEI is formed, simultaneously suppressing electrolyte consumption and excessive SEI growth.

Mechanism and industrial potential

Using operando Raman spectroscopy and molecular dynamics (MD) simulations, the researchers identified the mechanism by which an anion-rich environment forms at the electrode surface during battery operation, leading to the formation of a stable inorganic SEI.

This technology requires only the addition of a thin surface layer without altering electrolyte composition, offering high compatibility with existing manufacturing processes and minimal cost burden. In particular, the iCVD process enables large-area, continuous roll-to-roll production, making it suitable for industrial-scale mass production beyond the laboratory.

Professor Jinwoo Lee stated, "Beyond developing new materials, this study is significant in that it presents a design principle showing how electrolyte reactions and interfacial stability can be controlled through electrode surface engineering. This technology can accelerate the commercialization of anode-free lithium metal batteries in next-generation high-energy battery markets such as electric vehicles and energy storage systems (ESS)."

This research was conducted with Ph.D. candidate Juhyun Lee, and postdoctoral Jinuk Kim, a postdoctoral researcher from the Department of Chemical and Biomolecular Engineering at KAIST, serving as co–first authors. 

Anode-free lithium metal batteries, which have attracted attention as candidates for electric vehicles, drones, and next-generation high-performance batteries, offer much higher energy density than conventional lithium-ion batteries. However, their short lifespan has made commercialization difficult.

KAIST researchers have now moved beyond conventional approaches that required repeatedly changing electrolytes and have succeeded in dramatically extending battery life through electrode surface design alone.

A research team led by Professors Jinwoo Lee and Sung Gap Im of the Department of Chemical and Biomolecular Engineering fundamentally resolved the issue of interfacial instability—the greatest weakness of anode-free lithium metal batteries—by introducing an ultrathin artificial polymer layer with a thickness of 15 nanometers (nm) on the electrode surface.

The results are published in Joule.

How anode-free batteries work

Anode-free lithium metal batteries have a simple structure that uses only a copper current collector instead of graphite or lithium metal at the anode. This design offers advantages such as 30–50% higher energy density compared to conventional lithium-ion batteries, lower manufacturing costs, and simplified processes. 

Provided by The Korea Advanced Institute of Science and Technology (KAIST) 

by The Korea Advanced Institute of Science and Technology (KAIST)

edited by Sadie Harley, reviewed by Robert Egan 

Source: Ultrathin polymer layer extends lifespan of anode-free lithium metal batteries