First fluorescent probe for graphite anodes of lithium-ion

Uneven lithium intercalation and plating in graphite anodes severely affect the capacity decay and lifetime of lithium-ion batteries (LIBs). Visual and quantitative detection on the amount, distribution, and morphology of active lithium in/upon the graphite anodes is important for analyzing the performance and failure of anodes. Here, we design a novel solid-state fluorescence probe, TPECatechol, for graphite anodes. TPECatechol has a dual responsiveness to graphite anodes: a SWITCH of fluorescence wavelength and intensity when meeting active lithium or a complete QUENCH when touching graphite. Based on this, TPECatechol realized not only the visual observation of the nonuniform distribution of lithium intercalation and morphology of lithium plating but also a quantitative measurement of state of charge (SOC) of graphite anodes based on the different fluorescence intensities. The solid-state fluorescence imaging can reflect the actual condition of cycled anodes from real pouch batteries and provide a valid experimental means for understanding the electrochemical processes of LIBs.