Deciphering the Role of Fluorination in Dual-Halogen Electrolytes for All-Solid-State Batteries: A Case Study of New Li2HfCl6−xFx Solid Electrolytes

Lanting Qian; Yubo Wang; Jue Liu; Ivan Kochetkov; Ning Chen; Cameron Dean; Linda F. Nazar

doi:10.1002/anie.202509209

Deciphering the Role of Fluorination in Dual-Halogen Electrolytes for All-Solid-State Batteries: A Case Study of New Li₂HfCl_6−xF_x Solid Electrolytes

Lanting Qian
, Yubo Wang
, Jue Liu
, Ivan Kochetkov
, Ning Chen
, Cameron Dean
, Linda F. Nazar

Powder Diffraction

Research output: Contribution to journal › Article › peer-review

4 Scopus citations

Abstract

Lithium metal chlorides are promising superionic conductors for all-solid-state batteries (SSBs) due to their favorable mechanical properties, high ionic conductivity, and good oxidative stability (up to >4.2 V versus Li/Li⁺). Nonetheless, chloride solid electrolytes (SEs) still undergo electrochemical degradation when paired with high-voltage cathodes such as LiNi_0.85Co_0.1Mn_0.05O₂. A viable strategy to enhance the intrinsic electrochemical stability of chloride electrolytes is to partially substitute Cl with F. By leveraging complementary insights from neutron and X-ray diffraction, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and electrochemical studies, we investigate the interplay between ionic and electronic conductivity, voltage stability, and overall battery performance of a family of new dual-halogen SEs—Li₂HfCl_6−xF_x. All-solid-state cells utilizing Li₂HfCl_5.5F_0.5 as the electrolyte demonstrate much-enhanced battery performance compared to Li₂HfCl₆. This improvement is mainly attributed to the formation of a kinetically stable LiF-rich cathode electrolyte interphase (CEI), which inhibits detrimental reactions between the cathode and the SE, as revealed by ToF-SIMS studies. The findings from this study are applicable to other dual-halogen solid ionic conductors, offering valuable insights into the relationship between intrinsic electrochemical window (IEW), electronic and ionic conductivity, and battery performance in dual-halogen solid-state electrolytes.

Original language	English
Article number	e202509209
Journal	Angewandte Chemie - International Edition
Volume	64
Issue number	41
DOIs	https://doi.org/10.1002/anie.202509209
State	Published - Oct 6 2025

Funding

L.F.N thanks the Ontario Research Fund (ORF-RE) for financial support and NSERC for platform support through the Discovery Grant and Canada Research Chair program. All authors gratefully acknowledge Compute Canada for CPU allocations and Dr. Baltej Singh (UWaterloo) for valuable discussions regarding the computational aspects of this work. L.Q acknowledges NSERC for providing a graduate fellowship. Hard X-ray XAS data Hf L3-edge was collected at the Hard X-ray Micro-Analysis (HXMA) beamline, and soft X-ray XANES for F K-edge Spherical Grating Monochromator (SGM) beamline at the Canadian Light Source. The neutron data were collected at the NOMAD beamline at ORNL's Spallation Neutron Source, which is sponsored by the Scientific User Facilities Division, Office of Basic Sciences, U.S. Department of Energy. They thank Dr. Peter Brodersen for recording the ToF-SIMS data at the Ontario Centre for the Characterization of Advanced Materials (OCCAM) at the University of Toronto and Dr Zachary Arthur at the Canadian Light Source for collecting the soft X-ray data. L.F.N thanks the Ontario Research Fund (ORF‐RE) for financial support and NSERC for platform support through the Discovery Grant and Canada Research Chair program. All authors gratefully acknowledge Compute Canada for CPU allocations and Dr. Baltej Singh (UWaterloo) for valuable discussions regarding the computational aspects of this work. L.Q acknowledges NSERC for providing a graduate fellowship. Hard X‐ray XAS data Hf L3‐edge was collected at the Hard X‐ray Micro‐Analysis (HXMA) beamline, and soft X‐ray XANES for F K‐edge Spherical Grating Monochromator (SGM) beamline at the Canadian Light Source. The neutron data were collected at the NOMAD beamline at ORNL's Spallation Neutron Source, which is sponsored by the Scientific User Facilities Division, Office of Basic Sciences, U.S. Department of Energy. They thank Dr. Peter Brodersen for recording the ToF‐SIMS data at the Ontario Centre for the Characterization of Advanced Materials (OCCAM) at the University of Toronto and Dr Zachary Arthur at the Canadian Light Source for collecting the soft X‐ray data.

Keywords

Interphases
Lithium metal chloride electrolytes
Solid-state batteries
Solid-state electrolytes
ToF-SIMS

Access to Document

10.1002/anie.202509209

Cite this

@article{6f11ed0e15c9453ca2840de113528ad0,

title = "Deciphering the Role of Fluorination in Dual-Halogen Electrolytes for All-Solid-State Batteries: A Case Study of New Li2HfCl6−xFx Solid Electrolytes",

abstract = "Lithium metal chlorides are promising superionic conductors for all-solid-state batteries (SSBs) due to their favorable mechanical properties, high ionic conductivity, and good oxidative stability (up to >4.2 V versus Li/Li+). Nonetheless, chloride solid electrolytes (SEs) still undergo electrochemical degradation when paired with high-voltage cathodes such as LiNi0.85Co0.1Mn0.05O2. A viable strategy to enhance the intrinsic electrochemical stability of chloride electrolytes is to partially substitute Cl with F. By leveraging complementary insights from neutron and X-ray diffraction, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and electrochemical studies, we investigate the interplay between ionic and electronic conductivity, voltage stability, and overall battery performance of a family of new dual-halogen SEs—Li2HfCl6−xFx. All-solid-state cells utilizing Li2HfCl5.5F0.5 as the electrolyte demonstrate much-enhanced battery performance compared to Li2HfCl6. This improvement is mainly attributed to the formation of a kinetically stable LiF-rich cathode electrolyte interphase (CEI), which inhibits detrimental reactions between the cathode and the SE, as revealed by ToF-SIMS studies. The findings from this study are applicable to other dual-halogen solid ionic conductors, offering valuable insights into the relationship between intrinsic electrochemical window (IEW), electronic and ionic conductivity, and battery performance in dual-halogen solid-state electrolytes.",

keywords = "Interphases, Lithium metal chloride electrolytes, Solid-state batteries, Solid-state electrolytes, ToF-SIMS",

author = "Lanting Qian and Yubo Wang and Jue Liu and Ivan Kochetkov and Ning Chen and Cameron Dean and Nazar, \{Linda F.\}",

note = "Publisher Copyright: {\textcopyright} 2025 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.",

year = "2025",

month = oct,

day = "6",

doi = "10.1002/anie.202509209",

language = "English",

volume = "64",

journal = "Angewandte Chemie - International Edition",

issn = "1433-7851",

publisher = "wiley",

number = "41",

}

TY - JOUR

T1 - Deciphering the Role of Fluorination in Dual-Halogen Electrolytes for All-Solid-State Batteries

T2 - A Case Study of New Li2HfCl6−xFx Solid Electrolytes

AU - Qian, Lanting

AU - Wang, Yubo

AU - Liu, Jue

AU - Kochetkov, Ivan

AU - Chen, Ning

AU - Dean, Cameron

AU - Nazar, Linda F.

PY - 2025/10/6

Y1 - 2025/10/6

N2 - Lithium metal chlorides are promising superionic conductors for all-solid-state batteries (SSBs) due to their favorable mechanical properties, high ionic conductivity, and good oxidative stability (up to >4.2 V versus Li/Li+). Nonetheless, chloride solid electrolytes (SEs) still undergo electrochemical degradation when paired with high-voltage cathodes such as LiNi0.85Co0.1Mn0.05O2. A viable strategy to enhance the intrinsic electrochemical stability of chloride electrolytes is to partially substitute Cl with F. By leveraging complementary insights from neutron and X-ray diffraction, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and electrochemical studies, we investigate the interplay between ionic and electronic conductivity, voltage stability, and overall battery performance of a family of new dual-halogen SEs—Li2HfCl6−xFx. All-solid-state cells utilizing Li2HfCl5.5F0.5 as the electrolyte demonstrate much-enhanced battery performance compared to Li2HfCl6. This improvement is mainly attributed to the formation of a kinetically stable LiF-rich cathode electrolyte interphase (CEI), which inhibits detrimental reactions between the cathode and the SE, as revealed by ToF-SIMS studies. The findings from this study are applicable to other dual-halogen solid ionic conductors, offering valuable insights into the relationship between intrinsic electrochemical window (IEW), electronic and ionic conductivity, and battery performance in dual-halogen solid-state electrolytes.

AB - Lithium metal chlorides are promising superionic conductors for all-solid-state batteries (SSBs) due to their favorable mechanical properties, high ionic conductivity, and good oxidative stability (up to >4.2 V versus Li/Li+). Nonetheless, chloride solid electrolytes (SEs) still undergo electrochemical degradation when paired with high-voltage cathodes such as LiNi0.85Co0.1Mn0.05O2. A viable strategy to enhance the intrinsic electrochemical stability of chloride electrolytes is to partially substitute Cl with F. By leveraging complementary insights from neutron and X-ray diffraction, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and electrochemical studies, we investigate the interplay between ionic and electronic conductivity, voltage stability, and overall battery performance of a family of new dual-halogen SEs—Li2HfCl6−xFx. All-solid-state cells utilizing Li2HfCl5.5F0.5 as the electrolyte demonstrate much-enhanced battery performance compared to Li2HfCl6. This improvement is mainly attributed to the formation of a kinetically stable LiF-rich cathode electrolyte interphase (CEI), which inhibits detrimental reactions between the cathode and the SE, as revealed by ToF-SIMS studies. The findings from this study are applicable to other dual-halogen solid ionic conductors, offering valuable insights into the relationship between intrinsic electrochemical window (IEW), electronic and ionic conductivity, and battery performance in dual-halogen solid-state electrolytes.

KW - Interphases

KW - Lithium metal chloride electrolytes

KW - Solid-state batteries

KW - Solid-state electrolytes

KW - ToF-SIMS

UR - https://www.scopus.com/pages/publications/105013768673

U2 - 10.1002/anie.202509209

DO - 10.1002/anie.202509209

M3 - Article

C2 - 40831399

AN - SCOPUS:105013768673

SN - 1433-7851

VL - 64

JO - Angewandte Chemie - International Edition

JF - Angewandte Chemie - International Edition

IS - 41

M1 - e202509209

ER -