Study on the Influence of Water Molecules on the Electrical Properties of the $\text{PE} / \text{Al}\left(\begin{array}{lll}0 & 0 & 1\end{array}\right)$ and $\text{PE} / \text{Al}$ (100) Interfaces

The aluminum/polyethylene (AI/PE) interface is a critical structure in high-voltage cables, where space charge injection and accumulation are closely associated with the formation of the electric double layer (EDL) at the interface, playing a vital role in the cable's insulating properties. However, the underlying physical mechanisms, particularly at the molecular level, remain poorly understood. In order to elucidate the effect of EDL at the PE/AI interface, we systematically investigated the effect of different EDL structures and water molecules on the potential distribution and interfacial barrier at the AI-PE interface based on first principle calculations. In addition, the potential barrier between Al and PE was calculated using PBE and PBE0 hybrid functionals for both (10 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0)$</tex> and (001) surfaces of AI. The results show that the potential distribution in the Al layer is largely unaffected by the EDL variation, while the potential in the PE layer is significantly modulated, which is mainly due to the built-in electric field generated by the EDL. When water molecules are added to the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{PE} / \text{Al}$</tex> interface, they have little effect on the interface barrier. In this study, the influence of EDL on the AI/PE interface barrier was deeply investigated to provide a theoretical basis for improving the insulation performance of high-voltage cables.