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Manipulated Fluoro‐Ether Derived Nucleophilic Decomposition Products for Mitigating Polarization‐Induced Capacity Loss in Li‐Rich Layered Cathode

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Abstract and Figures

Electrolyte engineering is a fascinating choice to improve the performance of Li‐rich layered oxide cathodes (LRLO) for high‐energy lithium‐ion batteries. However, many existing electrolyte designs and adjustment principles tend to overlook the unique challenges posed by LRLO, particularly the nucleophilic attack. Here, we introduce an electrolyte modification by locally replacing carbonate solvents in traditional electrolytes with a fluoro‐ether. By benefit of the decomposition of fluoro‐ether under nucleophilic O‐related attacks, which delivers an excellent passivation layer with LiF and polymers, possessing rigidity and flexibility on the LRLO surface. More importantly, the fluoro‐ether acts as “sutures”, ensuring the integrity and stability of both interfacial and bulk structures, which contributed to suppressing severe polarization and enhancing the cycling capacity retention from 39 % to 78 % after 300 cycles for the 4.8 V‐class LRLO. This key electrolyte strategy with comprehensive analysis, provides new insights into addressing nucleophilic challenge for high‐energy anionic redox related cathode systems.
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Batteries
Manipulated Fluoro-Ether Derived Nucleophilic Decomposition
Products for Mitigating Polarization-Induced Capacity Loss in Li-
Rich Layered Cathode
Baodan Zhang, Haitang Zhang, Haiyan Luo, Haiming Hua, Xiaohong Wu, Yilong Chen,
Shiyuan Zhou, Jianhua Yin, Kang Zhang, Hong-Gang Liao, Qingsong Wang, Yeguo Zou,*
Yu Qiao,* and Shi-Gang Sun
Abstract: Electrolyte engineering is a fascinating choice
to improve the performance of Li-rich layered oxide
cathodes (LRLO) for high-energy lithium-ion batteries.
However, many existing electrolyte designs and adjust-
ment principles tend to overlook the unique challenges
posed by LRLO, particularly the nucleophilic attack.
Here, we introduce an electrolyte modification by
locally replacing carbonate solvents in traditional elec-
trolytes with a fluoro-ether. By benefit of the decom-
position of fluoro-ether under nucleophilic O-related
attacks, which delivers an excellent passivation layer
with LiF and polymers, possessing rigidity and flexibility
on the LRLO surface. More importantly, the fluoro-
ether acts as “sutures”, ensuring the integrity and
stability of both interfacial and bulk structures, which
contributed to suppressing severe polarization and
enhancing the cycling capacity retention from 39 % to
78% after 300 cycles for the 4.8 V-class LRLO. This key
electrolyte strategy with comprehensive analysis, pro-
vides new insights into addressing nucleophilic challenge
for high-energy anionic redox related cathode systems.
Introduction
In the pursuit of next-generation lithium-ion batteries
(LIBs) to power portable electronics and electric vehicles,
there is an urgent need for competitive cathodes with high
energy density.[1] Lithium-rich layer oxides (LRLO) cath-
odes have emerged as attractive candidates for cathode
materials due to their outstanding energy density (>
1000 Wh/kg).[2] Unlike conventional cathodes, LRLO
achieves a considerable portion of its capacity through
oxygen redox reactions under high potential (>4.4 V vs. Li/
Li+).[3] While this elevated anion capacity is advantageous
during sustained charging, it introduces another challenge at
the LRLO interface, i.e., nucleophilic attack,[4] especially
from oxygen-related nucleophilic species that can severely
affect the stability of electrolytes.[5] Distinguishing from
typical NiCoMn systems (LiNi0.5Mn0.5O4, NCM811, etc.),[6]
the interfacial stability of LRLO is threatened not only by
high-voltage electrochemical oxidation but also by nucleo-
philic attack from activated oxygen species.[7] Both electro-
chemical oxidation and nucleophilic attack can disrupt
electrolyte decomposition pathways and subsequently re-
shape the cathode-electrolyte interphase (CEI) architecture,
significantly affecting the stability of LRLO from the inter-
face to the bulk materials.[8] Unfortunately, practical strat-
egies for addressing these challenges related to electrolytes
in LRLO, including oxidative and nucleophilic threats, have
been largely overlooked,[9] leading to a dilemma in optimiz-
ing the electrochemical performance of LRLO cathode.
It is now confirmed that abundant oxygen-related
intermediate species are generated during high-voltage
oxidation in lithium-rich layer oxide cathodes.[10] These
intermediates include lattice oxygen ions (On), superoxo
(O2), peroxo (O2
2), oxygen vacancies (O-vacancies), O2
dimers, or lost O2, which pose a significant challenge to the
stability of the electrolyte and cathode-electrolyte interface
of LRLO.[11] In particular, nucleophilic species such as
peroxo and superoxo can preferentially react with certain
solvents,[12] altering the way CEI forms,[13] which is different
from a conventional high-voltage cathode.[14] Despite the
existence of both electrochemical oxidation and nucleophilic
attack in LRLO, mainstream electrolyte strategies have
generally followed the commonly used methods employed
for typical high-voltage cathodes that are not oxygen-
[*] B. Zhang, H. Zhang, H. Luo, H. Hua, Y. Chen, S. Zhou, J. Yin,
K. Zhang, H.-G. Liao, Y. Zou, Y. Qiao, S.-G. Sun
State Key Laboratory of Physical Chemistry of Solid Surfaces,
Collaborative Innovation Center of Chemistry for Energy Materials
(iChEM), Department of Chemistry, College of Chemistry and
Chemical Engineering, Xiamen University
Xiamen, 361005 (P. R. China)
E-mail: YeguoZou@outlook.com
yuqiao@xmu.edu.cn
B. Zhang, Y. Zou, Y. Qiao
Fujian Science & Technology Innovation Laboratory for Energy
Materials of China (Tan Kah Kee Innovation Laboratory)
Xiamen, 361005 (P. R. China)
X. Wu
Fujian Provincial Key Laboratory of Functional Materials and
Applications, Institute of Advanced Energy Materials, School of
Materials Science and Engineering, Xiamen University of Technol-
ogy
Xiamen, 361024 (P. R. China)
Q. Wang
Bavarian Center for Battery Technology (BayBatt), Department of
Chemistry, University of Bayreuth
95447 Bayreuth (Germany)
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How to cite: Angew. Chem. Int. Ed. 2024,63, e202316790
doi.org/10.1002/anie.202316790
Angew. Chem. Int. Ed. 2024,63, e202316790 (1 of 11) © 2023 Wiley-VCH GmbH
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