Stable Energy Storage Capacity of Polymer Dielectrics From −100°C to 200°C via Induced Carrier and Heat Suppression by Silica Aerogel

ABSTRACT The operating temperature range and reliability of dielectrics limit their advanced applications. We propose a strategy to broaden the operating temperature ranging from −100°C to 200°C with superior energy‐storage performance of polyetherimide (PEI) nanocomposites by incorporating silica aerogel with exceptional insulating and thermal‐barrier properties. The silica aerogel effectively eliminates filler agglomeration and reinforces mechanical strength. Benefiting from its ultra‐wide bandgap and excellent insulation, the silica aerogel acts as deep traps that suppress charge transport and reduce leakage current. Meanwhile, its intrinsic low thermal conductivity and porous framework serve as heat‐shielding units that elongate and distort the heat‐transfer pathway, effectively mitigating thermal conduction and accumulation. As a result, the silica aerogel/PEI nanocomposites achieve outstanding capacitive energy storage at a wide operating temperature range. Impressively, at −60°C, the nanocomposite delivers a discharge energy density (U dis ) of 12.54 J/cm 3 with an energy efficiency (η‌) of 96.8% at 900 MV/m. Even at 200°C, it maintains the U dis of 5.24 J/cm 3 with η >90%, representing 3.56 times higher than PEI. Moreover, the nanocomposites exhibit excellent reliability of over 10 6 charge‐discharge cycles at a wide temperature range. This work provides a new design paradigm for developing dielectrics with broad‐temperature energy storage capability.