Molecular structure conversion concomitant with mass transfer processes at the electrode-electrolyte interfaces plays a central role in energy electrochemistry. Mass spectrometry, as one of the most intuitive, sensitive techniques, provides the capability to collect transient intermediates and products and uncover reaction mechanisms and kinetics. In situ time-of-flight secondary ion electrochemical mass spectrometry with inherent high mass and spatiotemporal resolution has emerged as a promising strategy for investigating electrochemical processes at the electrode surface. This review illustrates the recent advancements in coupling time-of-flight secondary ion mass spectrometry and electrochemistry to visualize and quantify local dynamic electrochemical processes, identify solvated species distribution, and disclose hidden reaction pathways at the molecular level. Moreover, the key challenges in this field are further discussed to promote new applications and discoveries in operando studying the dynamic electrochemical interfaces of advanced energy systems.