UCl3-Type Solid Electrolytes: Fast Ionic Conduction and Enhanced Electrode Compatibility

Figure 1. Origin of the superionic conduction of UCl₃-type SEs with the non-close-packed framework. (a) Li⁺ probability density, represented by green isosurfaces from AIMD simulations in the vacancy-contained LaCl₃ lattice. Reproduced with permission from reference (21). Copyright 2023 the author(s), under exclusive license to Springer Nature Limited. (b) Schematic of diffusion channel. Reproduced with permission from reference (24). Copyright 2024 John Wiley and Sons. (c) Diffusion channel size distribution of Li₃YCl₆, Li₃InCl₆, LiNbOCl₄, and UCl₃-type Li_0.388Ta_0.238La_0.475Cl₃ (LTLC). Reproduced with permission from reference (24). Copyright 2024 John Wiley and Sons. (d) Schematic illustration of the effects of inherent distortion on energy landscape. Reproduced with permission from reference (24). Copyright 2024 John Wiley and Sons. Figure 2. Ionic conductivity values at room temperature of crystalline chloride SEs, including conventional close-packed Li_xM_yCl_n SEs and UCl₃-type LaCl₃-based SEs. (1−4,10−14,21) Reproduced with permission from reference (21). Copyright 2023 the author(s), under exclusive license to Springer Nature Limited. Figure 3. UCl₃-type SEs with a more stable interface toward lithium metal anode. (a) Depth-dependent La 3d_5/2 X-ray photoelectron spectroscopy (XPS) spectra of the interface of Li_0.388Ta_0.238La_0.475Cl₃ SE after 50 h of cycling. Reproduced with permission from reference (21). Copyright 2023 by Springer Nature Limited. (b) Depth-dependent La 3d_5/2 XPS spectra of the interface of Li_0.388Ta_0.238La_0.475Cl₃ SE after 50 h of cycling. Reproduced with permission from reference (21). Copyright 2023 the author(s), under exclusive license to Springer Nature Limited. (c) Voltage profile of a Li/Li_0.388Ta_0.238La_0.475Cl₃/Li symmetric cell cycled under a current density of 0.2 mA cm^–2 and areal capacity of 1 mAh cm^–2 at 30 °C. Insets: corresponding magnified voltage profiles indicate steady Li plating/stripping voltages. Reproduced with permission from reference (21). Copyright 2023 the author(s), under exclusive license to Springer Nature Limited. (d) La 3d_5/2 (left) and Zr 3d (right) XPS spectra of the Li|Li_0.8Zr_0.25La_0.5Cl_2.7O_0.3 interface after 500 h cycling, respectively. Reproduced with permission from reference (23). Copyright 2024 Royal Society of Chemistry. (e) Comparison of the critical current density (CCD) of Li metal symmetric cells with different solid electrolytes (Ga-LLZO (Li_6.4Ga_0.2La₃Zr₂O₁₂); LAGP (Li_1.5Al_0.5Ge_1.5(PO₄)₃); Ta-LLZO (Li_6.5La₃Zr_1.5Ta_0.5O₁₂); PEO:Mg(ClO) (PEO:Mg(ClO₄)₂); LiBFSIE-LLZO (LiBFSIE-Li₇La₃Zr₂O₁₂); PEO:LLZTO; O–LiPSBr(O-doped Li₆PS_4.7O_0.3Br); LiPS-0.5LiI (Li₃PS₄-0.5LiI); rod-like LiPSCl (Li₆PS₅Cl)). Reproduced with permission from reference (23). Copyright 2024 Royal Society of Chemistry. Density. The central elements (lanthanide metals La, Ce, Sm, etc.) and commonly used doping elements (Ta, Zr, etc.) for UCl₃-type SEs are heavy, often leading to a high density of UCl₃-type SEs over 2.5 g cm^–3, much higher than that of sulfides (usually less than 2 g cm^–3). To ensure a low weight ratio of nonactive materials in the cathode and SE layer in the whole solid battery for higher energy density, (31) doping elements with low atom numbers (e.g., Ca, Mg, and Al et al.) are preferred. Optimization in the anode stabilization mechanism. Though LaCl₃-based SEs have shown better interface compatibility with the lithium metal anode than conventional Li_xM_yCl_n, the stabilization mechanisms are still not thoroughly identified. Meanwhile, the capacity of around 1 mAh cm^–2 is insufficient to meet the demand of practical applications (usually over 3 mAh cm^–2). A deeper understanding of interface evolution, accompanied by an artificial interfacial layer to enhance anode interface stability, is needed. Atmosphere tolerance. Similar to conventional Li_xM_yCl_n, due to easy reaction or combination with water, (32) the atmosphere tolerance of UCl₃-type SEs needs enhancement to restrain the performance loss during synthesis, store, film-forming process and ASSLB fabrication. Y.C.Y, J.D.L, and H.B.Y discussed the topic and proposed the outline. Y.C.Y organized and wrote the draft. H.B.Y revised the manuscript. Yi-Chen Yin is now a postdoctoral researcher at the University of Science and Technology of China. He obtained his Bachelor’s degree from the China University of Mining and Technology in 2017 and his Ph.D. degree from the University of Science and Technology of China in 2022. His interests are in new halide solid electrolytes with high ionic conductivity and good electrode interface stability. Jin-Da Luo is now an M.S. candidate at the University of Science and Technology of China. He obtained his Bachelor’s degree from Xiangtan University in 2021. His research focuses on the computational modeling and simulation of ion transport within the lattice of solid electrolytes. Hong-Bin Yao received his BS degree from the University of Science and Technology of China in 2006. Then, he pursued his Ph.D. degree at the Hefei National Laboratory for Physical Sciences at the microscale under the supervision of Professor Shu-Hong Yu. After receiving his Ph.D. degree in 2011, he joined Professor Yi Cui’s group at Stanford University as a postdoc. In 2015, he finished his postdoc work and joined the University of Science and Technology of China as a professor. His group focuses on functional metal halide crystalline materials and related device applications. We acknowledge the financial support from the National Natural Science Foundation of China (Grant No. 22475235, 22325505, 52073271, 22305236), the USTC Research Funds of the Double First-Class Initiative (YD2060002034), the Collaborative Innovation Program of Hefei Science Center, CAS (Grant No. 2022HSC-CIP018), and the China Postdoctoral Science Foundation (Grant No. 2023M733375 and 2023T160619). This article references 32 other publications. This article has not yet been cited by other publications.