PROBING THE NATIVE STRUCTURE AND CHEMISTRY OF Li-METAL BATTERIES BY CRYO-ELECTRON MICROSCOPY

摘要

Processes at solid-liquid interfaces play an important role in many chemical, physical, and biological systems. For example, dendrite formation during charging of next-generation lithium metal batteries (LMBs) is closely tied to electrode-electrolyte interface processes, including breakdown of electrolyte to form a nanoscale solid-electrolyte interphase (SEI) layer [1]. The resulting dendrite growth leads to a rapid capacity fade and safety issues [2]. Practical rechargeable LMBs have therefore been elusive, despite their improved energy density over Li-ion batteries. While scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) can provide structure and bonding information down to the atomic-scale and have proven invaluable for understanding processes at solid-solid interfaces [3], accurate characterisation of complex and buried interfaces such as those between electrodes and electrolytes is challenging. LMB interfaces introduce additional complications, since lithium metal is highly reactive and commonly used liquid electrolytes are volatile in vacuum. To address the buried nature of the interface and electrolyte volatility, typically the liquid is removed by washing and drying prior to traditional characterisation, which can considerably alter the interface structure and chemistry. The ability to directly probe the inherent nanoscale structure and chemistry of these interfaces would significantly aid our understanding and control of the processes that occur there.