关键词: 锂离子电池, 锂金属, 针刺, 短路, 热失控

Abstract:

Although lithium-ion batteries are widely adopted, their safety remains a critical bottleneck that limits further technological advancement. This study investigates how anode materials influence the thermal runaway pathways of ternary pouch cells by examining the safety responses of graphite and lithium metal anodes under nail penetration and external short-circuit conditions. By simultaneously monitoring key parameters, including temperature, voltage, current, and analyzing electrode interface morphology and contact status, this study demonstrates that anode properties fundamentally affect failure mechanisms during thermal events. In external short-circuit tests, the highly reactive lithium metal anode, together with powdery lithium deposits formed after cycling, exacerbates exothermic side reactions, resulting in significantly higher peak currents (148.7 A vs. 100.9 A) and maximum temperatures (273 ℃ vs. 104 ℃) than those observed with graphite anode, indicating a substantially greater risk of thermal runaway. Conversely, lithium metal anodes exhibit superior safety performance during nail penetration tests. Localized melting at the penetration site, along with subsequent physical detachment and rapid chemical passivation, leads to a sharp increase in contact resistance (>40 Ω), which effectively interrupting interrupts the internal short circuit and prevents thermal runaway. In contrast, the rigid structure of graphite anodes maintains the short-circuit pathway, causing rapid heat accumulation, with peak temperature rates exceeding 420 ℃/s. Overall, this study reveals the structure-property-failure relationship between anode materials and their associated thermal behaviors, providing valuable insights for the design of lithium batteries that combine high energy density with enhanced safety through targeted anode modification.

Key words: lithium-ion battery, lithium metal, nail penetration, short circuit, thermal runaway