Operando and in situ transmission electron microscopy: exploring real-time nanoscale phenomena of battery materials
Calliope Bazioti
University of Oslo
The growing global societal challenges addressed in the UN sustainable development goals Affordable and Clean Energy and Climate action trigger the need to upgrade technology related to sustainable energy storage, essential for the much-needed green shift to renewable energy production. In this respect, research efforts are focused on the development and fundamental understandings of new materials and their successful integration into modern technologies. However, due to materials’ operational complexity, instability and air sensitivity, post-mortem and ex-situ characterization techniques do not reveal the full scope of their operating mechanism, hindering their future development and commercial deployment. Hence, in situ and operando studies to observe materials’ evolution in real-time is the most promising route to acquire meaningful information. Recent advances in (Scanning) Transmission Electron Microscopy ((S)TEM) and microfabrication open up a new era for in situ and operando studies of materials and devices at the nanoscale. In particular, in situ sample holders have witnessed an impressive advancement with the introduction of microelectromechanical-based chips, enabling novel experiments to be performed. Combined with state-of-the-art microscopes, it is possible to obtain atomically-resolved data from materials exposed to precise heating, electrical biasing and various gas or liquid environments. Furthermore, there are possibilities to use chips specifically designed for battery-test setups and to integrate nano-machining and micro-manipulation capabilities of Focused Ion Beam, opening up new exciting possibilities to miniaturize real-life devices.
In this study, we present an example of in situ and operando (S)TEM investigations of M2C-type MXenes -a newly discovered class of 2D materials- promising as anodes for all-solid-state Li-ion batteries [1]. In situ gas-heating (S)TEM experiments were performed to achieve bottom-up growth -imitating the CVD process at the nanoscale- and gain fundamental understanding of the growth mechanisms of MXenes. A miniature of an all-solid-state working battery is demonstrated and an operando (S)TEM study revealing the real-time atomistic evolution of electrodes/electrolyte during cycling. Finally, a discussion of the recent advances in the development of liquid closed-cells follows, opening opportunities for operando (S)TEM experiments by mimicking the real battery environment. An example of SnX-anodes for stationary Na-ion batteries will demonstrate the unparallel insight into the unravelled details of the operating mechanism of conversion-alloying materials. All investigations were conducted on a probe-corrected and monochromated FEI Titan G2 60-300 kV supported by the NORTEM facility at the University of Oslo.
[1] S. Ravuri et al 2024 Nanotechnology 35 155601