Seeing is believing: in situ/operando optical microscopy for probing electrochemical energy systems

This review discusses a range of in situ/operando techniques based on optical microscopy reported in literatures for studying electrochemical energy systems. Compared to other techniques (scanning probe microscopy, electron microscopy, X-ray microscopy), optical microscopy offers many advantages including the simplicity of the instrument and operation, cost effectiveness, and nondestructive nature. In the past few decades, significant advances in the field of optical microscopy have been made, enabling new opportunities of more elaborate studies on electrochemical energy systems. Herein, different methodologies are compared, with the emphasis on experimental setup designs and findings, to illustrate their aptness.