CIC Energigune, Parque Tecnológico de Álava, C/Albert Einstein 48, 01510, Miñano, Spain.
IKERBASQUE, Basque Foundation for Science , Maria Diaz de Haro 3, 48013, Bilbao, Spain.
ACS Appl Mater Interfaces. 2017 Feb 1;9(4):3808-3816. doi: 10.1021/acsami.6b13925. Epub 2017 Jan 20.
All-solid-state batteries including a garnet ceramic as electrolyte are potential candidates to replace the currently used Li-ion technology, as they offer safer operation and higher energy storage performances. However, the development of ceramic electrolyte batteries faces several challenges at the electrode/electrolyte interfaces, which need to withstand high current densities to enable competing C-rates. In this work, we investigate the limits of the anode/electrolyte interface in a full cell that includes a Li-metal anode, LiFePO cathode, and garnet ceramic electrolyte. The addition of a liquid interfacial layer between the cathode and the ceramic electrolyte is found to be a prerequisite to achieve low interfacial resistance and to enable full use of the active material contained in the porous electrode. Reproducible and constant discharge capacities are extracted from the cathode active material during the first 20 cycles, revealing high efficiency of the garnet as electrolyte and the interfaces, but prolonged cycling leads to abrupt cell failure. By using a combination of structural and chemical characterization techniques, such as SEM and solid-state NMR, as well as electrochemical and impedance spectroscopy, it is demonstrated that a sudden impedance drop occurs in the cell due to the formation of metallic Li and its propagation within the ceramic electrolyte. This degradation process is originated at the interface between the Li-metal anode and the ceramic electrolyte layer and leads to electromechanical failure and cell short-circuit. Improvement of the performances is observed when cycling the full cell at 55 °C, as the Li-metal softening favors the interfacial contact. Various degradation mechanisms are proposed to explain this behavior.
全固态电池包括石榴石陶瓷电解质，是替代目前使用的锂离子技术的潜在候选材料，因为它们具有更安全的操作和更高的储能性能。然而，陶瓷电解质电池的发展在电极/电解质界面面临着几个挑战，这些界面需要承受高电流密度以实现有竞争力的 C 率。在这项工作中，我们研究了包括锂金属阳极、LiFePO4 阴极和石榴石陶瓷电解质的全电池中阳极/电解质界面的极限。发现阴极和陶瓷电解质之间添加液态界面层是实现低界面电阻和充分利用多孔电极中活性材料的先决条件。在最初的 20 个循环中，从阴极活性材料中提取出可重复和恒定的放电容量，这表明石榴石作为电解质和界面的效率很高，但长时间循环会导致电池突然失效。通过使用结构和化学特性表征技术，如 SEM 和固态 NMR 以及电化学和阻抗谱，证明由于金属 Li 的形成及其在陶瓷电解质中的传播，电池中的阻抗突然下降。这种降解过程起源于锂金属阳极和陶瓷电解质层之间的界面，并导致机电故障和电池短路。当全电池在 55°C 下循环时，观察到性能的改善，因为锂金属的软化有利于界面接触。提出了各种降解机制来解释这种行为。
