The development of solid electrolytes with superior electrical and electrochemical performances for the room-temperature operation of sodium (Na)-based batteries is at the infant stage and still remains a challenge. Herein, we, for the first time, report hybrid solid electrolytes consisting of PEO₂₀–NaClO₄–5% SiO₂–x% Emim FSI (x = 50, 70) designed for solid-state Na-metal batteries. The hybrid design yields a solid electrolyte featuring a high room-temperature ionic conductivity of 1.3 × 10⁻³ S cm⁻¹, suitable mechanical property, a wide voltage stability window of 4.2 V and a high Na⁺ transference number of 0.61. A prototypical Na-metal battery using this hybrid solid electrolyte demonstrates promising long-term cycling performances at room temperature and at an elevated temperature of 60 °C for 100 cycles. The finding implies that the hybrid solid electrolyte is promising for Na-metal batteries operating at room temperature.

To reveal the mechanism of energy storage in the water/graphene system and water/grapheme-oxide system, the processes of rapid evaporation of water molecules on the sheets of graphene and graphene-oxide are investigated by molecular dynamics simulations. The results show that both the water/graphene and water/grapheme-oxide systems can store more energy than the pure water system during evaporation. The hydroxyl groups on the surface of graphene-oxide are able to reduce the attractive interactions between water molecules and the sheet of graphene-oxide. Also, the radial distribution function of the oxygen atom indicates that the hydroxyl groups affect the arrangement of water molecules at the water/graphene-oxide interface. Therefore, the capacity of thermal energy storage of the water/graphene-oxide system is lower than that of the water/graphene system, because of less desorption energy at the water/graphene-oxide interface. Also, the evaporation rate of water molecules on the graphene-oxide sheet is slower than that on the graphene sheet. The Leidenfrost phenomenon can be observed during the evaporation process in the water/grapheme-oxide system.