Fluorescence Probing of Active Lithium Distribution for Lithium Metal Anode

Uncontrollable growth of Li dendrites and accumulation of "dead Li" are two severe concerns for lithium (Li) metal battery, which leads to safety hazards and low Coulombic efficiency, respectively. To investigate the deterioration behavior of cell, it is of great importance to illustrate the distribution of active Li species on anode surface and distinguish the Li dendrites from the dead Li species. However, up to date, it is still challenging to identify these issues by conventional visual observation methods. In this work, we introduced a novel fluorescent probing strategy employing 9,10-dimethylanthracene (DMA). Through marking the cycled Li anode surface, the active Li distribution can be visualized by virtue of the fluorescence quenching reaction of DMA with the active Li. This method demonstrates validity for electrolyte selection and predictive detection of uneven Li deposition for Li metal anode. Furthermore, the location of dendrites and dead Li species can be clearly identified after destructive (e.g. high current density) utilization of Li metal anode, which will contribute to the development of failure analysis technology for Li metal battery applications.