Vema Sundeep, Sayed Farheen N, Nagendran Supreeth, Karagoz Burcu, Sternemann Christian, Paulus Michael, Held Georg, Grey Clare P
Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
The Faraday Institution, Quad One, Harwell Campus, Didcot OX11 0RA, United Kingdom.
ACS Energy Lett. 2023 Jul 20;8(8):3476-3484. doi: 10.1021/acsenergylett.3c01042. eCollection 2023 Aug 11.
Garnet solid-electrolyte-based Li-metal batteries can be used in energy storage devices with high energy densities and thermal stability. However, the tendency of garnets to form lithium hydroxide and carbonate on the surface in an ambient atmosphere poses significant processing challenges. In this work, the decomposition of surface layers under various gas environments is studied by using two surface-sensitive techniques, near-ambient-pressure X-ray photoelectron spectroscopy and grazing incidence X-ray diffraction. It is found that heating to 500 °C under an oxygen atmosphere (of 1 mbar and above) leads to a clean garnet surface, whereas low oxygen partial pressures (i.e., in argon or vacuum) lead to additional graphitic carbon deposits. The clean surface of garnets reacts directly with moisture and carbon dioxide below 400 and 500 °C, respectively. This suggests that additional CO concentration controls are needed for the handling of garnets. By heating under O along with avoiding HO and CO, symmetric cells with less than 10 Ωcm interface resistance are prepared without the use of any interlayers; plating currents of >1 mA cm without dendrite initiation are demonstrated.
基于石榴石固态电解质的锂金属电池可用于具有高能量密度和热稳定性的储能装置。然而，石榴石在环境气氛中表面形成氢氧化锂和碳酸锂的趋势带来了重大的加工挑战。在这项工作中，通过使用两种表面敏感技术，即近常压X射线光电子能谱和掠入射X射线衍射，研究了各种气体环境下表面层的分解情况。研究发现，在氧气气氛（1毫巴及以上）下加热到500°C会得到清洁的石榴石表面，而低氧分压（即在氩气或真空中）会导致额外的石墨碳沉积。石榴石的清洁表面分别在400°C以下和500°C以下直接与水分和二氧化碳发生反应。这表明在处理石榴石时需要额外控制CO浓度。通过在O下加热并避免HO和CO，制备出了界面电阻小于10Ωcm的对称电池，且未使用任何中间层；展示了大于1 mA cm的镀覆电流且无枝晶萌生。
