Pearl‐Chain‐Embedded Architecture in Polyimide‐Based Hybrid Aerogel Membranes: Toward Flexible Thermal Protection for Lithium‐Ion Batteries

ABSTRACT Thermal protection in confined electronic spaces, particularly within lithium‐ion battery packs, faces a persistent conflict: materials must be thin enough to maximize energy density yet robust enough to block heat propagation. To resolve this, we developed a “pearl‐chain‐embedded” polyimide‐silica aerogel membrane via a tailored two‐step gelation strategy. By strictly controlling the interfacial chemistry, we employed hydroxyl‐containing polyimide chains to establish a dense hydrogen‐bonding network with the in situ‐grown silica. This molecular‐level engineering yields a hybrid membrane that decouples flexibility from thermal stability—retaining mechanical integrity after 1000 folding cycles (bending radius: 3 mm) while suppressing the severe high‐temperature shrinkage typical of pure organic aerogels. Critically, in practical safety tests, a layer merely 1 mm thick established a sufficient thermal barrier to block the chain reaction of battery thermal runaway. These findings present a robust pathway for designing ultrathin safety layers in next‐generation lithium‐ion batteries.