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Quantifying Phase Transformations in Alloying Anodes via in-situ Liquid Cell Hard X-ray Spectroscopy and Cryogenic Microscopy

Neil Mulcahy1, Syeda Ramin Jannat1, Yaqi Li1, Tigran Simonian1, Mariana Palos1, James O. Douglas1, Jessica M. Walker2, Baptiste Gault1,3,4, Mary P. Ryan1 et al.

Michele Shelly Conroy1,*

  • *Contact author: m.conroy@imperial.ac.uk
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PRX Energy 5, 033009 – Published 12 August, 2026

DOI: https://doi.org/10.1103/r3tc-hr17

Abstract

Understanding electrochemical phenomena at complex liquid-solid interfaces requires linking real-time structural dynamics with atomic-scale interfacial chemistry. Here, we integrate in-situ synchrotron X-ray fluorescence and diffraction with high-resolution cryogenic electron and ion multimodal microscopy to provide a mechanistic understanding of Pt-based alloying anodes across length scales. We directly observe the initial lithiation-driven formation of Li2Pt and its evolution to a stable LiPt intermetallic phase during extended cycling via a solid-solution type reaction mechanism. Simultaneously, the solid-electrolyte interphase transitions from an unstable carbonate-rich to a stable LiF-dominated composition, confirmed by cryogenic scanning transmission electron microscopy-electron energy loss spectroscopy. Crucially, cryogenic atom probe tomography reveals spatially distinct compositional regimes within the alloy anode: a lithium-flux-limited, heterogeneous interfacial zone and a diffusion-controlled, homogeneous LiPt alloy bulk. This nanoscale compositional gradient rationalizes the emergent solid-solution reaction mechanism and highlights how kinetic limitations and interface dynamics govern alloy formation and electrochemical stability. Our findings establish a correlative experimental framework that directly links in-situ structural dynamics with preserved near-atomic resolution interfacial chemistry, advancing the rational design of durable alloy electrodes for next-generation energy storage.

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Popular Summary

Batteries power everything from mobile devices to electric vehicles, yet many promising electrode materials fail because they break down at the interfaces where the liquid electrolyte meets the solid electrode. Understanding what happens at these buried interfaces during battery operation is extremely difficult, especially as materials change their structure and chemistry in real time.

In this work, the authors bring together several advanced experimental tools to follow how platinum-based alloy anodes evolve as a battery charges and discharges. Using high-energy X-rays, cryogenic electron imaging, and atomic scale chemical mapping, they track how lithium moves into the alloy, how new phases form, and how the protective surface layer develops. The authors discover that the alloy does not transform all at once. Instead, lithium accumulates unevenly near the interface, creating a nanoscale gradient that controls how the alloy forms and how stable it becomes.

By linking fast structural changes with near-atomic-resolution chemical information, this approach provides a new way to understand complex battery interfaces. These insights can guide the design of longer-lasting alloy electrodes and can help accelerate the development of next-generation energy storage technologies.

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PRX Energy 5, 033009– Published 12 August, 2026
  • Received 4 December 2025
  • Revised 8 April 2026
  • Accepted 9 June 2026
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