Batteries with lithium metal anodes have been viewed as one of the most promising candidates for the next generation of electrochemical energy storage devices. Researchers have made tremendous effort to fulfill a high areal capacity utilization of lithium metal anode and coupled it with high voltage cathode. In this way, the battery life (calculated from energy density) can be more than doubled in the future.
However, safety concerns and short lifespan hinder the further application of lithium metal. These issues arise from the uneven lithium plating/stripping process during battery cycling, which leads to the formation of lithium dendrites and ‘deal’ lithium.
Although both dendrites (penetrating through the separator and subsequently leading to safety issue) and dead lithium (leading to short lifespan) can kill a battery, we need to differentiate them for understanding these failure processes and finding solution. However, since the morphology was quite similar in both cases, conventional observation methods can not identify the distribution of them on lithium metal anode.
For this target, researchers from Prof. CUI Guanglei Group at the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT), Chinese Academy of Sciences (CAS) have proposed a new approach with the assistance of a fluorescence dye to direct observe the distribution of active lithium species on the lithium metal.
The fluorescence dye is 9,10-dimethylanthracene (DMA). The solution of DMA can form a uniform coverage on lithium anode and react with lithium, leading to fluorescence quenching. Therefore, areas with active lithium becomes dark, particularly the sites with dendrites, while the surfaces covered by thick byproducts retain the fluorescence.
By employing this fluorescence probing method, it is possible to identify the particular sites of dendrites directly through fluorescence microscopy, which would help to optimize the structure of cell and offer new insight for electrolyte selection in lithium metal battery application.
The related findings were published in Angew. Chem. Int. Ed. The research was supported by Strategic Priority Research Program of the Chinese Academy of Sciences, the National Key R&D Program of China Natural Science Foundation of China, Natural Science Foundation of Shandong, and Youth Innovation Promotion Association of CAS.
Fig: Schematic illustration of DMA probing measurement. (Image by CHENG Xiangyang)
