Smart Construction of an Intimate Lithium | Garnet Interface for All‐Solid‐State Batteries by Tuning the Tension of Molten Lithium

• Published in: Advanced functional materials 2021-08, Vol.31 (31), p.n/a
• Main Authors: Du, Mingjie, Sun, Yang, Liu, Bo, Chen, Bingbing, Liao, Kaiming, Ran, Ran, Cai, Rui, Zhou, Wei, Shao, Zongping
• Format: Article
• Language: English
• Subjects: Critical current density; cycling stability; Dendritic structure; Electric contacts; Electric vehicles; Electrolytes; Extreme values; Flux density; garnet electrolytes; Impedance; interfacial impedance; Ion currents; Li depositing; Lithium; Lithium batteries; Materials science; Molten salt electrolytes; Point contact; Product safety; solid batteries; Solid electrolytes; Surface tension; Tuning
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202101556

All‐solid‐state lithium batteries (ASSBs) have the potential to trigger a battery revolution for electric vehicles due to their advantages in safety and energy density. Screening of various possible solid electrolytes for ASSBs has revealed that garnet electrolytes are promising due to their high ionic conductivity and superior (electro)chemical stabilities. However, a major challenge of garnet electrolytes is poor contact with Li‐metal anodes, resulting in an extremely large interfacial impedance and severe Li dendrite propagation. Herein, an innovative surface tension modification method is proposed to create an intimate Li | garnet interface by tuning molten Li with a trace amount of Si3N4 (1 wt%). The resultant Li‐Si‐N melt can not only convert the Li | garnet interface from point‐to‐point contact to consecutive face‐to‐face contact but also homogenize the electric‐field distribution during the Li stripping/depositing process, thereby significantly decreasing its interfacial impedance (1 Ω cm2 at 25 °C) and improving its cycle stability (1000 h at 0.4 mA cm−2) and critical current density (1.8 mA cm−2). Specifically, the all‐solid‐state full cell paired with a LiFePO4 cathode delivered a high capacity of 145 mAh g−1 at 2 C and maintained 97% of the initial capacity after 100 cycles at 1 C. Molten Li shrinks easily into droplets and results in poor contact with garnet electrolytes. A new class of Li‐Si‐N melts with low surface tension are designed to create intimate Li | garnet interfaces, enabling ultralow interfacial impedance, a fast charge‐discharge rate, and significantly enhanced cyclability of all‐solid‐state Li symmetric and full batteries.