Zakaria Mohamed Barakat, Nagata Takahiro, Chikyow Toyohiro
International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
Department of Chemistry, Faculty of Science, Tanta University, Tanta, Gharbeya 31527, Egypt.
ACS Omega. 2019 Aug 30;4(12):14680-14687. doi: 10.1021/acsomega.9b01095. eCollection 2019 Sep 17.
Mesoporous hafnium dioxide (HfO) thin films (around 20 nm thick) were fabricated by a sol-gel-based spin-coating process, followed by an annealing process at 600 °C to realize the ion-conducting media for the ionics (e.g., Na and K for rechargeable ion batteries). Another film of aluminum metal (10 nm thick) was deposited by direct current sputtering to soak into the mesopores. A monitored thermal treatment process at 500 °C in the air yields mesostructured HfO/AlO composite thin films. However, aluminum dioxide (AlO) is formed during annealing as an insulating film to reduce the leakage current while retaining the ionic conductivity. The obtained mesostructured HfO/AlO films show a leakage current at 3.2 × 10 A cm, which is significantly smaller than that of the mesoporous HfO film (1.37 × 10 A cm) or HfO/Al film (0.037 A cm) at a bias voltage of 1.0 V, which is enough for ion conduction. In the meantime, among all the thin films, the mesostructured HfO/AlO composite thin films display the smallest Nyquist arc diameter in 1.0 M KOH electrolyte, implying a lower impedance at the electrode/electrolyte interface and reflecting a better ion diffusion and movement.
通过基于溶胶 - 凝胶的旋涂工艺制备了厚度约为20 nm的介孔二氧化铪（HfO）薄膜，随后在600°C下进行退火处理，以实现用于离子学的离子传导介质（例如，用于可充电离子电池的Na和K）。通过直流溅射沉积另一层厚度为10 nm的铝金属薄膜，使其浸入介孔中。在空气中500°C下进行的监测热处理过程产生了介孔结构的HfO/AlO复合薄膜。然而，在退火过程中会形成作为绝缘膜的氧化铝（AlO），以降低漏电流，同时保持离子导电性。所获得的介孔结构的HfO/AlO薄膜在1.0 V偏置电压下的漏电流为3.2×10 A/cm，这明显小于介孔HfO薄膜（1.37×10 A/cm）或HfO/Al薄膜（0.037 A/cm）的漏电流，这对于离子传导来说已经足够。与此同时，在所有薄膜中，介孔结构的HfO/AlO复合薄膜在1.0 M KOH电解质中显示出最小的奈奎斯特弧直径，这意味着在电极/电解质界面处具有较低的阻抗，并反映出更好的离子扩散和移动。
