School of Materials Science and Engineering, Tongji University, Shanghai, 201804, China.
Institute of New Energy for Vehicles, Tongji University, Shanghai, 201804, China.
Adv Mater. 2018 Apr;30(17):e1706375. doi: 10.1002/adma.201706375. Epub 2018 Mar 22.
Lithium metal anodes are potentially key for next-generation energy-dense batteries because of the extremely high capacity and the ultralow redox potential. However, notorious safety concerns of Li metal in liquid electrolytes have significantly retarded its commercialization: on one hand, lithium metal morphological instabilities (LMI) can cause cell shorting and even explosion; on the other hand, breaking of the grown Li arms induces the so-called "dead Li"; furthermore, the continuous consumption of the liquid electrolyte and cycleable lithium also shortens cell life. The research community has been seeking new strategies to protect Li metal anodes and significant progress has been made in the last decade. Here, an overview of the fundamental understandings of solid electrolyte interphase (SEI) formation, conceptual models, and advanced real-time characterizations of LMI are presented. Instructed by the conceptual models, strategies including increasing the donatable fluorine concentration (DFC) in liquid to enrich LiF component in SEI, increasing salt concentration (ionic strength) and sacrificial electrolyte additives, building artificial SEI to boost self-healing of natural SEI, and 3D electrode frameworks to reduce current density and delay Sand's extinction are summarized. Practical challenges in competing with graphite and silicon anodes are outlined.
锂金属阳极在下一代高能量密度电池中具有很大的潜力，因为其具有极高的容量和极低的氧化还原电位。然而，由于锂金属在液体电解质中存在严重的安全问题，其商业化进程受到了显著阻碍：一方面，锂金属形态不稳定性（LMI）可能导致电池短路甚至爆炸；另一方面，生长的 Li 枝晶会引发所谓的“死 Li”；此外，液体电解质和可循环锂的不断消耗也缩短了电池寿命。研究界一直在寻求保护锂金属阳极的新策略，在过去十年中取得了重大进展。本文概述了对固体电解质界面（SEI）形成、概念模型以及 LMI 先进实时特性的基本认识。受概念模型的指导，总结了包括提高液体中可提供氟浓度（DFC）以增加 SEI 中 LiF 成分、提高盐浓度（离子强度）和牺牲电解质添加剂、构建人工 SEI 以促进天然 SEI 的自我修复，以及 3D 电极框架以降低电流密度和延迟沙的灭绝等策略。文中还概述了与石墨和硅阳极竞争的实际挑战。
