One primary cause of NEV fires is thermal runaway initiated by internal short
circuit in power batteries, leading to subsequent thermal diffusion throughout
the battery system. Severe internal short circuit damage can precipitate thermal
runaway phenomena in lithium-ion batteries, potentially culminating in fire
incidents involving electric vehicles. Although mild internal short circuit may
not immediately induce thermal runaway, continuous charge and discharge cycling
can exacerbate such conditions, progressively elevating risks associated with
thermal runaway and other pertinent safety hazards. Conventional safety testing
methodologies, employing techniques such as crushing and nail penetration to
simulate internal short circuit, often amplify the extent of these shorts and
fail to accurately replicate less severe, deeper internal short circuit.
Additionally, methods incorporating foreign objects like nickel pieces for
simulating internal short circuit necessitate battery disassembly, thereby
compromising structural integrity and impeding effective characterization. This
study introduces an innovative approach utilizing semi-insulated nails to
precisely trigger internal short circuit in lithium-ion batteries. This method
affords accurate control over the location of internal short circuit within the
battery, mitigating the exaggerated spread effect inherent to traditional nail
penetration techniques and enhancing the fidelity of internal short circuit
simulation. Despite the immediate risk of thermal runaway being relatively low
following precisely triggered internal short circuit, and external parameters
such as voltage and temperature showing no significant deviations from normal
batteries, undetected internal short circuit poses substantial latent risks to
the safety and performance of electric vehicles. These inconsistencies become
particularly pronounced under conditions of abuse, such as short circuits or
overcharging, wherein the safety performance diverges significantly from that of
unaffected batteries. Comparative analysis through overcharging and
short-circuit safety tests following traditional internal short circuit events
facilitates a more thorough investigation into safety reliability and failure
evolution, thereby elucidating the underlying discrepancies and associated
safety implications.