Detection of Micro-Scale Li Dendrite via H2 Gas Capture for Early Safety Warning

Li-ion battery safety issues related to fires and explosions are frequently triggered by Li dendrite growth, which is a predominant reason for separator piercing and cell shorts and is very difficult to detect in the early state. Here, we developed a sensitive detection method based on H2 gas capture that could detect trace amounts of Li dendrite formation. H2 gas was generated due to reaction of metallic Li with polymer binders. Even micron-scale Li dendrite (∼2.8 × 10−4 mg and 50 μm) growth can trigger H2 capture. Overcharge experiment with a LiFePO4-graphite battery pack (8.8 kWh) shows that H2 was captured first among H2, CO, CO2, HCL, HF, and SO2, and the capture time was 639 s earlier than smoke and 769 s earlier than fire. The Li dendrite growth can be completely prevented once H2 is captured, with neither smoke nor fire observed, which provides an effective method for early safety warning.