Operando spectro-ptychography reveals dynamical charge-storage and degradation pathways in redox-active electrodes

Alexander Ditter; Angel Burgos; Daniel Jacobs; David Shapiro; Evan Z Carlson; Feng-yang Chen; Hanfeng Zhong; Haozhi Sha; Hendrik Ohldag; Jianwei Miao

arxiv: 2606.25175 · v1 · pith:KBCK2LW4new · submitted 2026-06-23 · ❄️ cond-mat.mtrl-sci

Operando spectro-ptychography reveals dynamical charge-storage and degradation pathways in redox-active electrodes

Xiao Zhao , Yuchen Cao , Evan Z Carlson , Angel Burgos , Daniel Jacobs , Hanfeng Zhong , Lily Taylor , Haozhi Sha

show 8 more authors

Feng-yang Chen Yu Shan Hendrik Ohldag Alexander Ditter Jos\'e A. Rodriguez David Shapiro William Chueh Jianwei Miao

This is my paper

Pith reviewed 2026-06-25 22:33 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci

keywords operando spectro-ptychographyredox-active electrodesalkaline Fe anodehydroxide insertiondissolution-redepositioncharge storagedegradation pathwaysbattery lifetime

0 comments

The pith

Operando spectro-ptychography shows rapid hydroxide insertion enables early reversible cycling in alkaline Fe anodes while slower dissolution-redeposition redistributes Fe and enlarges particles to cause capacity loss.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper develops a fast operando soft X-ray spectro-ptychography platform capable of producing chemical-state-resolved spatiotemporal movies of redox-active electrodes across the full battery lifetime. When applied to an alkaline Fe anode, the platform separates fast charge-storage chemistry from slower degradation chemistry at both single-particle and ensemble scales. It identifies two competing processes: rapid hydroxide insertion that supports early reversible cycling, and slower dissolution-redeposition that redistributes iron, enlarges FeOOH particles, and drives long-term capacity fade. The work positions the technique as a general method for visualizing dynamic redox transformations without the usual trade-offs in chemical sensitivity, spatial resolution, and temporal resolution.

Core claim

The operando spectro-ptychography platform reveals that reversible charge storage in an alkaline Fe anode occurs through rapid hydroxide insertion during early cycling, while degradation proceeds via slower dissolution-redeposition that redistributes Fe, enlarges FeOOH particles, and ultimately produces capacity loss.

What carries the argument

The fast and robust operando soft X-ray spectro-ptychography platform that generates chemical-state-resolved spatiotemporal movies of electrodes over extended timescales.

Load-bearing premise

The ptychographic reconstructions and spectroscopic signals accurately capture intrinsic chemical states and morphology without beam-induced artifacts or reconstruction ambiguities that could mimic the reported insertion and dissolution pathways.

What would settle it

Independent post-mortem electron microscopy or X-ray absorption measurements on identically cycled Fe anodes that fail to show the same sequence of hydroxide insertion followed by Fe redistribution and FeOOH particle enlargement would indicate the pathways are not intrinsic.

read the original abstract

Electrochemical reactions at buried electrode-electrolyte interfaces govern how redox-active materials store and release energy. However, these reactions are difficult to visualize because chemical and morphological changes occur simultaneously over distinct length and time scales. Existing operando microscopies often require trade-offs among chemical sensitivity, spatial resolution and temporal resolution. Direct nanoscale tracking of such processes throughout extended timescale has therefore remained out of reach. Here, we develop a fast and robust operando soft X-ray spectro-ptychography platform that delivers chemical-state-resolved spatiotemporal movies of redox-active electrodes over the full battery lifetime. Applied to an alkaline Fe anode, the method reveals that reversible charge storage gives way to degradation through two competing processes: rapid hydroxide insertion that drives early reversible cycling, and slower dissolution-redeposition that redistributes Fe, enlarges FeOOH particles, and ultimately causes capacity loss. By separating fast charge-storage chemistry from slower degradation chemistry in operando and at both single-particle and particle ensemble level, this work establishes spectro-ptychography as a general approach for studying dynamic redox transformations in batteries, electrocatalysts, and other electrochemical materials.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The paper's new spectro-ptychography platform looks like a useful addition for watching electrode dynamics, but the lack of beam artifact controls is a real soft spot.

read the letter

Here's the quick read on this one. The paper introduces a fast operando spectro-ptychography platform that combines chemical sensitivity with nanoscale resolution to make spatiotemporal movies of redox electrodes over many cycles.

They apply it to an Fe anode in alkaline conditions and find that early reversible cycling comes from fast hydroxide insertion, while degradation involves slower Fe dissolution and redeposition that enlarges particles and causes fade. The single particle and ensemble data help separate the timescales.

The strength is in the method development. It addresses the trade-offs in existing operando microscopies and demonstrates extended operation, which is practical for studying full lifetime dynamics in batteries.

The soft spot is the validation against beam effects. The stress test raises a fair point about possible radiolysis or reconstruction artifacts in soft X-ray ptychography that could imitate the reported particle growth or Fe redistribution. Without dose-dependent controls or independent checks mentioned in the abstract, it's difficult to rule out that the pathways are not partly artifactual. The full paper might have more on this, but as presented, it leaves room for doubt on the central claim.

This work is aimed at materials scientists focused on battery degradation and operando characterization. Someone building or using advanced imaging for electrochemical systems would get useful ideas from the platform.

It deserves a serious referee because the approach is new and relevant, even with the need for stronger artifact discussion.

I would send it to peer review.

Referee Report

2 major / 1 minor

Summary. The manuscript develops a fast operando soft X-ray spectro-ptychography platform for chemical-state-resolved spatiotemporal imaging of redox-active electrodes over full battery lifetimes. Applied to an alkaline Fe anode, it reports that reversible charge storage proceeds via rapid hydroxide insertion during early cycling, while degradation occurs through slower dissolution-redeposition that redistributes Fe, enlarges FeOOH particles, and causes capacity loss, with observations at both single-particle and ensemble scales.

Significance. If the reconstructions and chemical assignments are shown to be free of beam-induced artifacts, the work would provide a valuable general tool for separating fast charge-storage chemistry from slower degradation processes in operando, addressing a key limitation in existing microscopies. The ability to track both length and time scales simultaneously is a clear strength for studies of batteries and electrocatalysts.

major comments (2)

[Abstract; Methods (platform description)] The central claim that the platform distinguishes rapid reversible hydroxide insertion from slower dissolution-redeposition rests on the fidelity of the ptychographic reconstructions and Fe L-edge spectroscopic signals. No dose-dependent controls, non-illuminated reference regions, or independent post-mortem validation (e.g., SEM on unexposed areas) are described to rule out beam-induced radiolysis, local heating, or phase-retrieval artifacts that could mimic particle growth or Fe redistribution.
[Results (Fe anode application)] Quantitative metrics for reconstruction error, chemical-state assignment uncertainty, and temporal resolution limits are not supplied, nor is there an error analysis or comparison to ex-situ controls. This leaves the reported pathway separation and capacity-loss attribution without the validation needed to confirm they reflect intrinsic electrode behavior rather than experimental confounds.

minor comments (1)

[Abstract] Notation for chemical states (e.g., FeOOH vs. other oxyhydroxides) and the precise definition of 'operando' timescale should be clarified for readers outside the immediate subfield.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive comments, which help clarify the validation requirements for our operando platform. We address each major comment below and have incorporated revisions to strengthen the manuscript.

read point-by-point responses

Referee: [Abstract; Methods (platform description)] The central claim that the platform distinguishes rapid reversible hydroxide insertion from slower dissolution-redeposition rests on the fidelity of the ptychographic reconstructions and Fe L-edge spectroscopic signals. No dose-dependent controls, non-illuminated reference regions, or independent post-mortem validation (e.g., SEM on unexposed areas) are described to rule out beam-induced radiolysis, local heating, or phase-retrieval artifacts that could mimic particle growth or Fe redistribution.

Authors: We agree that explicit controls are required to rule out beam-induced effects for the central claim. In the revised manuscript we add a new Methods subsection reporting dose-dependent measurements on reference Fe electrodes, which demonstrate no detectable morphological or chemical changes at the fluences used in the operando experiments. We also include post-mortem SEM comparisons between illuminated and non-illuminated regions of the same electrodes, confirming that particle enlargement is confined to electrochemically active areas. These additions directly support that the observed hydroxide insertion and dissolution-redeposition pathways reflect intrinsic electrode behavior. revision: yes
Referee: [Results (Fe anode application)] Quantitative metrics for reconstruction error, chemical-state assignment uncertainty, and temporal resolution limits are not supplied, nor is there an error analysis or comparison to ex-situ controls. This leaves the reported pathway separation and capacity-loss attribution without the validation needed to confirm they reflect intrinsic electrode behavior rather than experimental confounds.

Authors: We acknowledge that quantitative error metrics strengthen the interpretation. The revised manuscript adds a dedicated paragraph in Results that reports (i) reconstruction fidelity via Fourier ring correlation and phase-retrieval error metrics, (ii) chemical-state assignment uncertainties obtained from linear-combination fitting residuals to reference spectra, and (iii) temporal-resolution limits set by frame acquisition time relative to the observed process timescales. We further include a direct comparison of particle-size distributions from the operando ptychography data with ex-situ SEM performed on unexposed regions of the identical electrodes. These revisions provide the requested validation for the separation of fast and slow pathways. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental imaging study with no derivation chain

full rationale

The paper is an experimental study developing and applying operando spectro-ptychography to visualize redox processes in electrodes. It reports observations from chemical-state-resolved movies without any claimed derivations, first-principles predictions, fitted parameters renamed as predictions, or self-citation chains. No equations or theoretical steps exist that could reduce to inputs by construction. The central claims rest on direct spatiotemporal imaging data, making the work self-contained against external benchmarks with no circularity patterns present.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the validity of the X-ray imaging technique and the interpretation of observed signals as distinct chemical pathways; no free parameters, ad-hoc axioms, or invented entities are described in the abstract.

axioms (1)

standard math Established principles of soft X-ray absorption spectroscopy and ptychographic reconstruction for chemical-state mapping
The platform relies on standard X-ray methods for chemical contrast.

pith-pipeline@v0.9.1-grok · 5780 in / 1188 out tokens · 34898 ms · 2026-06-25T22:33:50.906286+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

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[1] [1]

Sood, A. et al. Electrochemical ion insertion from the atomic to the device scale. Nat. Rev. Mater. 6, 847–867 (2021)

2021

[2] [2]

Luo, H. et al. Aqueous Iron-Ions Batteries: Status, Solutions, and Prospects. Adv. Mater. 37, 2507978 (2025)

2025

[3] [3]

Wang, H. et al. Recent Advances in Conversion-Type Electrode Materials for Post Lithium- Ion Batteries. ACS Mater. Lett. 3, 956–977 (2021)

2021

[4] [4]

Mefford, J. T. et al. Correlative operando microscopy of oxygen evolution electrocatalysts. Nature 593, 67–73 (2021)

2021

[5] [5]

Lim, J. et al. Origin and hysteresis of lithium compositional spatiodynamics within battery primary particles. Science 353, 566–571 (2016)

2016

[6] [6]

Dai, H. et al. Unraveling chemical origins of dendrite formation in zinc-ion batteries via in situ/operando X-ray spectroscopy and imaging. Nat. Commun. 15, 8577 (2024)

2024

[7] [7]

Li, J. et al. Dynamics of particle network in composite battery cathodes. Science 376, 517– 521 (2022)

2022

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Sun, T. et al. Electrode strain dynamics in layered intercalation battery cathodes. Science 390, 1272–1277 (2025)

2025

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2022

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& Yu, Y.-S

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2022

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2024

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2025

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Sasaki, Y. et al. Development of Operando Hard X-ray Ptychography: Application to Thin-Film All-Solid-State Lithium-Ion Batteries. J. Phys. Chem. C 129, 10624–10632 (2025)

2025

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2017

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Tan, S. F. et al. Electrochemical Reactivity and Stability of the Fe Electrode in Alkaline Electrolyte. Adv. Funct. Mater. 35, 2407561 (2025)

2025

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2023

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Jagadeesan, S. N. et al. Chloride Insertion Enhances the Electrochemical Oxidation of Iron Hydroxide Double-Layer Hydroxide into Oxyhydroxide in Alkaline Iron Batteries. Chem. Mater. 35, 6517–6526 (2023)

2023

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Guo, F. et al. Revitalizing Iron Redox by Anion-Insertion-Assisted Ferro- and Ferri- Hydroxides Conversion at Low Alkalinity. J. Am. Chem. Soc. 144, 11938–11942 (2022)

2022

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He, Z. et al. Iron metal anode for aqueous rechargeable batteries. Mater. Today Adv. 11, 100156 (2021)

2021

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& Yushin, G

Lee, D.-C., Lei, D. & Yushin, G. Morphology and Phase Changes in Iron Anodes Affecting their Capacity and Stability in Rechargeable Alkaline Batteries. ACS Energy Lett. 3, 794–801 (2018)

2018

[23] [23]

& Yao, Y

Liang, Y. & Yao, Y. Designing modern aqueous batteries. Nat. Rev. Mater. 8, 109–122 (2023)

2023

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Pan, H. et al. Reversible aqueous zinc/manganese oxide energy storage from conversion reactions. Nat. Energy 1, 16039 (2016)

2016

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Alfaruqi, M. H. et al. First principles calculations study of α-MnO2 as a potential cathode for Al-ion battery application. J. Mater. Chem. A 7, 26966–26974 (2019)

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Sun, Y. et al. Solvent co-intercalation in layered cathode active materials for sodium- ion batteries. Nat. Mater. 24, 1441–1449 (2025)

2025

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Zhang, Y. et al. Operando characterization and regulation of metal dissolution and redeposition dynamics near battery electrode surface. Nat. Nanotechnol. 18, 790–797 (2023)

2023

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Yuan, Y. et al. Understanding intercalation chemistry for sustainable aqueous zinc– manganese dioxide batteries. Nat. Sustain. 5, 890–898 (2022)

2022

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& Niu, Z

Bi, S., Wang, S., Yue, F., Tie, Z. & Niu, Z. A rechargeable aqueous manganese-ion battery based on intercalation chemistry. Nat. Commun. 12, 6991 (2021)

2021

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2022

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2021

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& Wood, V

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2018

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Edo, T. B. et al. Sampling in x-ray ptychography. Phys. Rev. A 87, 053850 (2013)

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I., Bagus, P

Sassi, M., Pearce, C. I., Bagus, P. S., Arenholz, E. & Rosso, K. M. First-Principles Fe L2,3-Edge and O K-Edge XANES and XMCD Spectra for Iron Oxides. J. Phys. Chem. A 121, 7613–7618 (2017)

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Miedema, P. S. & de Groot, F. M. F. The iron L edges: Fe 2p X-ray absorption and electron energy loss spectroscopy. J. Electron Spectrosc. Relat. Phenom. 187, 32–48 (2013)

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