With the continuous increase in voltage levels of high-voltage direct current (HVDC) transmission, the requirements for the insulation properties of epoxy resin insulating materials have become increasingly stringent. However, existing methods for enhancing the insulation properties of epoxy resin through nanoparticle modification commonly face bottlenecks such as cumbersome processes, particle agglomeration, and weak interfacial bonding, making it difficult to achieve efficient and stable interfacial charge management. Herein, we report a reaction-induced in situ grafting strategy for nanoparticles. Using copper(II) diethyldithiocarbamate as a single-source precursor, Cu2S nanoparticles and tetraethylthiourea (TEU) surface-modifying molecules are simultaneously generated via its thermal decomposition reaction, achieving in situ chemical grafting of TEU onto the Cu2S surface. The resulting TEU@Cu2S functional nanoparticles were incorporated into the epoxy resin matrix, successfully constructing a stable ternary composite interface. The results demonstrate that this interface can suppress space charge accumulation by introducing deep-level charge traps, thereby significantly enhancing the DC breakdown strength and volume resistivity of the composite, while effectively reducing the surface charge accumulation density. This work provides an innovative and practical solution for the development of high-performance HVDC insulating materials.

Comprehending charge injection at the metal/epoxy interface is essential for designing and applying high-voltage electrical equipment. This study investigates surface charge accumulation in insulators used in high-voltage direct current (HVDC) gas-insulated switchgear (GIS), with a specific focus on the charge injection behavior at the metal/epoxy interface employing first-principles calculations. In this paper, two amine curing agents were selected to construct interface models of a Cu(111) slab and epoxy resin, with repeating fragments representing the crosslinked structure of the resin. Key parameters, including injection barriers, charge transfer, and vacuum energy level shifts (Δ), were evaluated. Notably, molecular structures containing -C₂F₆ bonds exhibited higher electron and hole injection barriers compared to those with -CH₂. Specifically, DDM induces reduced interfacial charge injection barriers and enhanced charge transport capabilities attributed to its low electronegativity and compact spatial configuration, whereas 6FDAM yields elevated barrier heights stemming from its strong electronegative character. The reliability of these findings was further validated through macroscopic charge injection experiments. The above study holds certain referential value for the development and application of high-voltage DC GIS equipment.