Department of Materials Science and Engineering, Stanford University , Stanford, California 94305, United States.
Institut für Mikro- und Nanostrukturforschung, Friedrich-Alexander-Universität Erlangen-Nürnberg , Cauerstrasse 6, 91058 Erlangen, Germany.
Nano Lett. 2017 Aug 9;17(8):5171-5178. doi: 10.1021/acs.nanolett.7b02630. Epub 2017 Jul 12.
Lithium (Li) metal is a high-capacity anode material (3860 mAh g) that can enable high-energy batteries for electric vehicles and grid-storage applications. However, Li metal is highly reactive and repeatedly consumed when exposed to liquid electrolyte (during battery operation) or the ambient environment (throughout battery manufacturing). Studying these corrosion reactions on the nanoscale is especially difficult due to the high chemical reactivity of both Li metal and its surface corrosion films. Here, we directly generate pure Li metal inside an environmental transmission electron microscope (TEM), revealing the nanoscale passivation and corrosion process of Li metal in oxygen (O), nitrogen (N), and water vapor (HO). We find that while dry O and N (99.9999 vol %) form uniform passivation layers on Li, trace water vapor (∼1 mol %) disrupts this passivation and forms a porous film on Li metal that allows gas to penetrate and continuously react with Li. To exploit the self-passivating behavior of Li in dry conditions, we introduce a simple dry-N pretreatment of Li metal to form a protective layer of Li nitride prior to battery assembly. The fast ionic conductivity and stable interface of Li nitride results in improved battery performance with dendrite-free cycling and low voltage hysteresis. Our work reveals the detailed process of Li metal passivation/corrosion and demonstrates how this mechanistic insight can guide engineering solutions for Li metal batteries.
锂（Li）金属是一种高容量的阳极材料（3860 mAh g），可用于为电动汽车和电网存储应用提供高能电池。然而，锂金属在暴露于液体电解质（在电池运行期间）或环境中时（在整个电池制造过程中）会高度反应并反复消耗。由于锂金属及其表面腐蚀膜的高化学反应性，在纳米尺度上研究这些腐蚀反应尤其困难。在这里，我们在环境透射电子显微镜（TEM）中直接生成纯锂金属，揭示了锂金属在氧气（O）、氮气（N）和水蒸气（HO）中的纳米级钝化和腐蚀过程。我们发现，虽然干燥的 O 和 N（99.9999 体积%）在 Li 上形成均匀的钝化层，但痕量的水蒸气（约 1 摩尔%）会破坏这种钝化并在 Li 金属上形成多孔膜，允许气体渗透并持续与 Li 反应。为了利用 Li 在干燥条件下的自钝化行为，我们在电池组装前对 Li 金属进行简单的干燥 N 预处理，形成一层氮化锂保护层。氮化锂具有快速的离子导电性和稳定的界面，可实现无枝晶循环和低电压滞后的电池性能改善。我们的工作揭示了 Li 金属钝化/腐蚀的详细过程，并展示了这种机械洞察力如何指导 Li 金属电池的工程解决方案。
