In operando nanothermometry by nanodiamond based temperature sensing

Precise evaluation of the temperature and its evolution at microscopic scale in an operating electrochemical device is essential for accessing the mechanism behind device performance for thermal management. However, such information is limited, as most of the existing temperature monitoring of electrochemical processes are carried out at macroscale. Fluorescent nanodiamond (ND) enables sensitive temperature monitoring at nanoscale in a working device without perturbing the electrochemical processes. In this study, we demonstrated spatially resolved temperature monitoring at nanoscale of a zinc (Zn) electroplating process, when temperature fluctuation in the device resulted from Zn dendrite-growth induced internal short circuit. We disclosed for the first time a significant difference in temperature measured at nanoscale by ND sensors and that at millimeter scale by a resistance temperature detector. Spatial temperature non-uniformity was found to persist during the entire Zn electroplating process, and a correlation between its evolution and the temperature fluctuation resulted from the current change was identified. This work represents an important step towards spatially resolved nanothermometry carried out in operando and precise evaluation on the local temperature and its evolution in a working electrochemical device.