Mechanochemically Disordered Oxyhalide Unlocks Superionic Conductivity
| Jerry Huang
Editor’s note： Solid electrolytes are the key component of all-solid-state lithium batteries (ASSLBs). Owing to their inherent safety, solid-state batteries are highly attractive energy-storage, yet their advancement hinges on breakthroughs in advanced solid electrolytes. Three principal families are currently available: inorganic electrolytes (including oxides, sulfides, and halides), organic polymer electrolytes (most commonly poly(ethylene oxide), PEO), and composite systems that integrate the two. Here is a new research from the team led by Jean-Marie Tarascon at the Collège de France. Inorganic solid electrolytes combine high ionic conductivity, excellent thermal stability, and a high Li⁺ transference number; they are therefore attracting ever-growing attention and are regarded as the cornerstone for the development of composite solid electrolytes. Experiment and computation attribute the superionic transport to disordering of the [Ta₂OCl₁₀]²⁻ dimers, to a reduction of the Li⁺ migration barrier, and to the enhanced spatial connectivity of Li⁺ diffusion pathways. Bilayer-electrolyte NMC811 full cells sustain more than 700 cycles at 1C, while simultaneously highlighting a practical limitation of this material—its insufficient reductive stability, which necessitates interfacial protection of the anode. An earlier research by Academician Xueliang Sun team at Eastern Institute of Technology Ningbo, had revealed high ionic conductivity by using another crystal Li3Ta3O4Cl10 in oxyhalide design. Thanks to all researchers for bringing promising superionic conductors in ASSLB designs.
Abstract
All-solid-state lithium-metal batteries (ASSBs) offer a promising route to surpass the energy-density limits of conventional lithium-ion technology. However, their commercialization is hindered by interfacial instability, chemo-mechanical degradation, and the limited ionic conductivity of current solid electrolytes, driving the search for new fast-ion conductors, particularly among lithium oxyhalides. Here, we report a new lithium tantalum oxychloride, Li2Ta2OCl10, synthesized via a simple low-temperature route. The material crystallizes in a triclinic structure composed of isolated [Ta2OCl10]2− dimers and exhibits a room-temperature ionic conductivity of 0.002 mS.cm−1. Ball milling dramatically enhances Li+ transport, increasing the conductivity by a factor of 5000 to 11 mS.cm−1 while reducing the activation energy from 0.46 to 0.27 eV. Combined structural, spectroscopic, and computational analyses reveal that this enhancement originates from the formation of a highly disordered, liquid-like Li+ sublattice. Li2Ta2OCl10 further demonstrates a stability window of 1.89–3.70 V vs. LixIn and enables ASSBs with low polarization and excellent capacity retention (700 cycles at 1C with decay less than 20%). These results establish Li2Ta2OCl10 as a promising superionic conductor and highlight the Li–M–O–Cl family as a fertile design space for next-generation solid electrolytes.
References
https://doi.org/10.1002/aenm.71736
https://www.science.org/doi/10.1126/science.adt9678