Journal Article

FZJ-2026-03152

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Synergistic Cu‐Fe Interactions Enhance Phase Transformation Kinetics Toward High‐Performance $CuFeS_2$ ‐Based All‐Solid‐State Batteries

Bai, C. ; Mazzio, K. A. (Corresponding author) ; Ruske, F. ; Srinivas, G. ; Bernges, T. ; Meng, J. ; Min, X. ; Sun, Y. ; Ahuja, V. ; Healy Corominas, R. ; Baran, V. ; Schuck, G. ; Haumann, M. ; Janek, J. ; Zeier, W. G.FZJ* ; Adelhelm, P. (Corresponding author)

2026
Wiley-VCH Weinheim

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Please use a persistent id in citations: doi:10.1002/adfm.76585  doi:10.34734/FZJ-2026-03152

Abstract: Chalcopyrite ($CuFeS_2$), composed of earth-abundant and environmentally benign elements, was synthesized via solid-state sintering of an equimolar $CuS$/$FeS$ mixture and evaluated as a cathode material for lithium all-solid-state batteries (ASSBs). $CuFeS_2$ was compared with a mixture of the $CuS$ and $FeS$ parent materials, which are theoretically expected to show similar conversion reaction products during lithiation. Galvanostatic cycling, XRD, XAS, SEM, and EDX analyses revealed that both samples undergo displacement reactions with lithium, leading to phase separation into $Cu^0$, $Fe^0$, and $Li_2S$. However, $CuFeS_2$ exhibits superior reversibility due to the formation of intermediate phases ($LiCuFeS_2$, $Li_3CuS_2$, $Li_2FeS_2$), where Cu-related phases may promote uniform Fe reactivation during charging. The synergistic Cu-Fe interactions improve reaction kinetics and reversibility, thereby enhancing overall electrochemical performance. In contrast, the CuS-FeS composite exhibits rapid capacity decay due to independent phase segregation and irreversible $Fe^0$ passivation. Electrochemically, $CuFeS_2$ delivers 207 $mAh g^{−1}$ with 61% retention after 100 cycles, outperforming $CuS$-$FeS$ (132 $mAh g^{−1}$, 40% retention). This work provides the most detailed mechanistic insight to date into the function of CuFeS2 in rechargeable Li cells and shows that controlled intermediate distribution and dynamically evolved conductive networks during phase transformation can improve conversion-type electrodes for ASSBs.

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Contributing Institute(s):

1. Helmholtz-Institut Münster Ionenleiter für Energiespeicher (IMD-4)

Research Program(s):

1. 1221 - Fundamentals and Materials (POF4-122) (POF4-122)

Appears in the scientific report 2026

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Database coverage:
; ; ; Clarivate Analytics Master Journal List ; Current Contents - Electronics and Telecommunications Collection ; Current Contents - Engineering, Computing and Technology ; Current Contents - Physical, Chemical and Earth Sciences ; DEAL Wiley ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 15 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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