Dynamic thermal response and degradation thresholds of vacuum insulation panels under lithium-ion battery thermal runaway

Vacuum insulation panels (VIPs) offer a promising passive thermal barrier for battery energy storage systems, yet the vacuum level required to effectively block thermal runaway (TR) propagation remains unclear. This study systematically investigates VIP thermal response under lateral heat conduction and vertical flame impingement across vacuum levels from −30 kPa to −98.5 kPa gauge, using 18,650 NCM cells. For lateral TR propagation, −35 kPa reduces the adjacent cell peak temperature from 117 °C to 65 °C, extends thermal lag by nearly 70%, and suppresses the post-venting heating rate. For vertical flame impingement from the safety vent, apparent performance transition −80 kPa is identified. Unexpectedly, further evacuation to −98.5 kPa leads to performance degradation, indicating a non-monotonic vacuum dependence that may arise from structural changes within the porous core, a non-monotonic effect contrary to conventional assumptions. Benchmarking against aerogel foam (AFP) and silica nano-aerogel blanket (SNB) shows AFP melts under flame (602 °C within 3 s), while SNB and VIP both limit the temperatures of the adjacent cell below 60 °C. A multi-criteria radar chart confirms VIP offers the most balanced profile among insulation, structural integrity, lightweight, cost, lifespan, and eco-safety. These findings provide actionable vacuum specifications: ≥ −35 kPa for lateral barriers and − 80 kPa for vent-facing protection, enabling reliable TR mitigation while avoiding over-engineering and reducing manufacturing costs.