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Enhancing ionic conductivity in solid electrolyte by relocating diffusion ions to under-coordination sites
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FULL TEST BANK Essential Cell Biology, 4th Edition 4th Edition by Bruce Alberts (Author) Graded A+ latest update.
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Test Bank for Essential Cell Biology, 4th Edition by Bruce Alberts, 9780815345251, Covering Chapters 1-20 | Includes Rationales
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Test Bank for Essential Cell Biology, 4th Edition by Bruce Alberts, 9780815345251, Covering Chapters 1-20 | Includes Rationales
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SCIENCE ADVANCES | RESEARCH ARTICLECHEMISTRY Copyright © 2022
The Authors, some
Enhancing ionic conductivity in solid electrolyte by rights reserved;
exclusive licensee
relocating diffusion ions to under-coordination sites American Association
for the Advancement
of Science. No claim to
Lei Zhu1†, Youwei Wang2,3†, Junchao Chen1,4†*, Wenlei Li5, Tiantian Wang2,3, Jie Wu1, original U.S. Government
Songyi Han1, Yuanhua Xia6, Yongmin Wu1, Mengqiang Wu5, Fangwei Wang7, Yi Zheng1, Works. Distributed
Luming Peng4, Jianjun Liu2,3,8*, Liquan Chen7, Weiping Tang1,9* under a Creative
Commons Attribution
Solid electrolytes are highly important materials for improving safety, energy density, and reversibility of electro- NonCommercial
chemical energy storage batteries. However, it is a challenge to modulate the coordination structure of conduct- License 4.0 (CC BY-NC).
ing ions, which limits the improvement of ionic conductivity and hampers further development of practical solid
electrolytes. Here, we present a skeleton-retained cationic exchange approach to produce a high-performance
solid electrolyte of Li3Zr2Si2PO12 stemming from the NASICON-type superionic conductor of Na3Zr2Si2PO12. The
introduced lithium ions stabilized in under-coordination structures are facilitated to pass through relatively large
conduction bottlenecks inherited from the Na3Zr2Si2PO12 precursor. The synthesized Li3Zr2Si2PO12 achieves a low
activation energy of 0.21 eV and a high ionic conductivity of 3.59 mS cm−1 at room temperature. Li3Zr2Si2PO12 not
only inherits the satisfactory air survivability from Na3Zr2Si2PO12 but also exhibits excellent cyclic stability and
rate capability when applied to solid-state batteries. The present study opens an innovative avenue to regulate
cationic occupancy and make new materials.
INTRODUCTION such as Li7La3Zr2O12 (10) and LiPON (11) usually exhibit higher elec-
All-solid-state batteries (ASSBs) are attracting ever increasing at- trochemical stability at the interface in working potentials (12). Despite
tention for solving the intrinsic drawbacks of current Li-ion batteries, tremendous research advancements in oxide solid electrolytes, it
such as leakage and flammability of liquid electrolytes, and limited still faces a large challenge to further improve their ionic conductivity
energy densities (1, 2). The success of ASSBs depends on solid electro- to meet the requirement of practicable application (13).
Downloaded from https://www.science.org on September 11, 2022
lytes with satisfying Li-ionic conductivities. A high electrochemical In the past decades, a great deal of effort has been made for de-
stability at the interface of the solid electrolytes with electrode ma- veloping oxide solid electrolytes such as LISICON (14), NASICON
terials in a wide range of working potentials also plays an important (15, 16), perovskite (17, 18), garnet (10, 19), and LiPON (20) sys-
role in designing ASSBs, for any electrochemical instability of solid tems. The basic step in diffusion paths is Li-ion migration between
electrolytes may result in interfacial decomposition products with a two stable sites through the high-energy transition state. In these
low ionic conductivity (3, 4). Recent studies on ASSBs have made compounds, Li-ions usually occupy the lower-energy hexahedral sites
considerable progress in high-conductivity inorganic solid electro- and commonly surmounting high-energy and narrow bottleneck
lytes, which are generally classified into sulfide and oxide solid elec- (transition state) into tetrahedral sites (Fig. 1A). Reducing the acti-
trolytes (5). The most remarkable features of sulfide solid electrolytes vation energy heights of transition states along the long-range dif-
such as Li10GeP2S12 (6) and Li6PS5X (X = Cl, Br, I) (7, 8) are their fusion path is of much importance in increasing ionic conductivity.
high ionic conductivity, comparable with organic liquid electrolytes For many years, optimization of these solid electrolytes has largely
at room temperatures, but low stability against Li metal to decom- proceeded by substituting skeleton structural elements to enlarge
pose into interfacial side product of Li2S (9). Oxide solid electrolytes the bottleneck and reduce the migration barrier (3, 21), which only
achieve the ionic conductivities of the order of 10−6 to 10−3 S cm−1
1
at room temperature and the activation energy of 0.25 to 0.6 eV.
State Key Laboratory of Space Power-Sources Technology, Shanghai Institute of
Space Power-Sources, Shanghai 200245, China. 2State Key Laboratory of High Per- Achieving a low migration barrier requires the bottleneck between
formance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, two different polyhedrons to satisfy a very specific size. Statistical
Chinese Academy of Sciences, Shanghai 200050, China. 3Center of Materials Science analysis indicates that those NASION-type lithium solid electrolytes
and Optoelectronics Engineering, College of Materials Science and Optoelectronic
Technology, University of Chinese Academy of Sciences, Beijing 100049, China.
with a bottleneck size of >2.05 Å exhibit a much lower migration
4
Key Laboratory of Mesoscopic Chemistry of MOE and Collaborative Innovation barrier (Fig. 1B) (22). Intrinsically, regulating bottleneck size corre-
Center of Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, sponds to change of polyhedron size, which may lead to Li+ occu-
Nanjing University, Nanjing 210023, China. 5Center for Advanced Electric Energy pancy changes from high-coordination to under-coordination sites
Technologies, School of Materials and Energy, University of Electronic Science and
Technology of China, Chengdu 611731, China. 6Key Laboratory of Neutron Physics, for retaining structural stabilization (Fig. 1C). Therefore, the regu-
Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, lating coordination structure between Li+ ions and O2− anions pro-
Mianyang 621999, China. 7Beijing National Laboratory for Condensed Mater vides an important strategy for breaking through this contradiction
Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
8
School of Chemistry and Materials Science, Hangzhou Institute for Advanced Study,
between occupancy stability and ionic conductivity.
University of Chinese Academy of Science, Hangzhou 310024, China. 9School of In this work, a skeleton-retained cationic exchange approach
Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai based on Na3Zr2Si2PO12 (NZSP) is proposed to synthesize advanced
200240, China. solid electrolyte Li3Zr2Si2PO12 (LZSP), in which Li+ ions self-adaptively
*Corresponding author. Email: cjcnuaa@163.com (J.C.); jliu@mail.sic.ac.cn (J.L.);
tangweiping@vip.sina.com (W.T.) occupy under-coordinated sites and maintain relatively large bottle-
†These authors contributed equally to this work. neck sizes by inheriting the pristine framework. The obtained LZSP
Zhu et al., Sci. Adv. 8, eabj7698 (2022) 18 March 2022 1 of 12
, SCIENCE ADVANCES | RESEARCH ARTICLE
A Expanded frame B
0.65
NASICON
0.60 LiGe2(PO4)3
LiGeTi(PO4)3
0.55
Migration barrier (eV)
LiGe0.5Ti1.5(PO4)3
0.50
LiTi2(PO4)3
0.45
High coordination Under-coordination
C 0.40
0.35 Li1.3Al0.3Ti1.7(PO4)3
LiSn2(PO4)3
LiHf2(PO4)3
0.30
LiZr2(PO4)3
0.25
1.90 1.95 2.00 2.05 2.10 2.15 2.20
Bottleneck (Å)
Fig. 1. Relationships among coordination modulation, bottleneck, and migration energy barrier. (A) Structural schematic of coordination engineering for the
transition between LiO6 hexahedrons and LiO4 tetrahedrons. (B) Migration barrier of Li+ ions from LiO6 hexahedrons to LiO4 adjacent tetrahedrons. (C) Relations between
bottleneck and the migration energy barrier of lithium-ion in NASICON-type lithium solid electrolytes (22).
is quite distinct from the low-ionic conductivity LiZr2(PO4)3 system, Li+ cation coordinating with the N element of the TFSI− anion),
which is prepared by the common sol-gel method or solid-state respectively] should be satisfied: (i) The selected liquid carrier (EMIIM
method with a high calcination temperature of 900° to 1200°C in this work) is capable of dissolving the lithium compound (LiTFSI
(12, 23, 24). In combination with electrochemical impedance spec- in this work) and simultaneously would not dissolve the solid electro-
Downloaded from https://www.science.org on September 11, 2022
troscopy (EIS) and density functional theory (DFT) calculations, we lyte precursor; (ii) except for cation exchange, no other chemical
demonstrate that the designed LZSP material with under-coordination reaction takes place. EMIIM and LiTFSI are selected as the solution
Li-ions achieves a bulk ionic conductivity of up to 3.59 × 10−3 S cm−1 environment and lithium source, respectively, to drive the cation
at room temperature and further performs excellent electrochemical, exchange process. The operation temperature and concentration
thermal, and air stability, which shows potential promising for practical difference are intrinsically two key driving forces for promoting the
application. The present work opens an innovative avenue to design cation substitution. Therefore, optimizing concentration difference
new solid electrolytes by skeleton-retained cationic exchange approach. and operation temperature is of great importance to balance in ex-
change effectiveness and damaging the skeleton of the solid electro-
lyte precursor due to inadequate and excessive additive. As shown
RESULTS in fig. S1, Na+ ions inside NZSP are thoroughly replaced by Li+ ions
Synthesis and local coordination of Li+ ions within LiTFSI dissolved EMIIM at 453 K (NZSP is not soluble in
The NASICON-type superionic conductor NZSP has both relatively EMIIM). Unlike the commonly adopted molten salt ion-exchange
high sodium ionic conductivity, ~10−4 S cm−1, and excellent struc- method that requires high-temperature calcination (>673 K) (28),
tural stability with strong resistance against air and exceptional this approach can be conducted at a relatively low temperature (≤453 K),
thermal stability (25, 26). Previous studies reveal that two-thirds of giving rise to the ability to restrain phase transition and keep the
Na+ ions occupy the hexa-coordinated sites in the NZSP lattice pristine framework. The usage of liquid carrier, ionic liquid—an
structure, while the others occupy the octa-coordinated sites (25). essential Li+ ionic conductor, enables the fast removal of Na+ ions
In the three-dimensional (3D) channels enclosed by SiO44−/PO43− and continuous entry of Li+ ions, where liquids without ionic con-
and ZrO68− polyhedrons, the hexa-coordinated Na+ ions contribute ductivity (e.g., water) may fail. In addition, the NZSP powders are
to the ionic conductivity by following the migration path of occu- more readily dispersed evenly in ionic liquids than solidified Li+
pied octahedrons and unoccupied tetrahedrons. However, the octa- carrier, which further facilitates the Li+/Na+ ionic exchange.
coordinated Na+ ions perform poor transport activity. Therefore, the The textures of “precursor” NZSP and “product” LZSP nano-
structure-stable NZSP is used as a precursor to synthesize the corre- crystals are determined by diffraction techniques and Rietveld re-
sponding solid electrolyte of LZSP through a skeleton-retained finement analysis (Fig. 2). The refined powder synchrotron x-ray
cationic exchange approach. diffraction (XRD) and neutron powder diffraction (NPD) patterns
The sodium superionic conductor NZSP was synthesized by a of NZSP and LZSP nanopowders (Fig. 2, A and B) crystallize with a
sol-gel method (27). To accomplish full cationic exchange from Na+ monoclinic phase, which belongs to the crystal group of C12/c1
to Li+, two basic principles about the selection and usage of solid (space group #15). In the locally amplified synchrotron XRD patterns
electrolyte precursor, liquid carrier, and lithium compound [NZSP, in Fig. 2A (see untruncated data in fig. S2), the peaks of (200) and
1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (400) as well as the (020) and (021) facets all shift to higher angles
(EMIIM), and bis(trifluoromethane) sulfonimide lithium (LiTFSI; from NZSP to LZSP, manifesting the lattice contraction of the a and
Zhu et al., Sci. Adv. 8, eabj7698 (2022) 18 March 2022 2 of 12
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