Visualized Detection of Lithium Plating on Graphite Anodes Cycled Under Low Temperature and Fast Charging

Abstract Lithium‐ion batteries are currently the most widely used electrochemical energy storage devices. However, the most used graphite anode faces severe lithium plating issues when charging at low temperatures or high rates, leading to battery's capacity decay and even safety concerns. Therefore, visually and quantitatively detecting lithium plating is extremely important to analyze battery's performances. Here a convenient, rapid‐response, visual, and semi‐quantitative technique, namely fluorescence probe, is put forward to visually and quantitatively detect lithium plating on graphite anodes. A commercially available aggregation‐induced emission (AIE) molecule (4′‐hydroxychalcone) is introduced as a probe. The hydroxyl group of 4′‐hydroxychalcone can rapidly and sensitively react with plated lithium, instantaneously emerging an intensive yellow fluorescence within seconds; while 4′‐hydroxychalcone undergoes fluorescence quenching when directly contacting with graphite. Based on this, not only the uneven distribution of plated lithium on graphite anodes can be simply and clearly visualized and detected after being charged at low temperatures or high rates, but also the semi‐quantitative relationship between fluorescence intensity and the amount of plated lithium can be well established. Therefore, this work puts forward a practical solution for analyzing lithium plating on graphite anodes, offering a practical approach for failure analysis of lithium‐ion batteries used in various scenarios.