Bio‐Inspired Continuous Gradient Nanocomposites for Ultrahigh‐Temperature Dielectric Energy Storage at 150°C–200°C

Dielectric polymers commonly suffer from severe performance degradation above 150°C, hindering advanced power systems. Herein, we demonstrate a polyetherimide (PEI) nanocomposite that overcomes this by mimicking the gradient architecture of nacre and bamboo, incorporating a continuous vertical gradient of fluorinated boron nitride nanosheets (BNNS‐F) through sequential electrospinning. This bio‐inspired design not only reinforces mechanical and thermal stability, but also generates a spatially gradient distribution of deep charge traps. The resulting progressive trap energy barrier effectively suppresses charge transport, impedes electrical treeing propagation, and significantly reduces conduction losses at elevated temperatures. Consequently, our continuous gradient PEI/BNNS‐F cg nanocomposite achieves an exceptional breakdown strength ( E b ) of 626 MV m −1 and a discharged energy density ( U d ) of 6.21 J cm −3 with 90% efficiency at 150°C, surpassing most reported polymer‐based dielectrics. Remarkably, it retains a high U d of 3.89 J cm −3 at 200°C, along with outstanding cycling stability over 10,000 cycles. This work introduces a new paradigm for controlling charge dynamics through continuous gradient structures, enabling high‐performance energy storage under extreme conditions.