Stable Interface Between Si-Negative Electrode and Oxide-Based Solid Electrolyte

Li6.6La3Zr1.6Ta0.4O12 (LLZT) disk with a flat and smooth surface was used as a model solid electrolyte to quantitatively evaluate Li+ transfer resistance at an interface between an LLZT solid electrolyte and a silicon electrode. The Li+ transfer process at the solid/solid interface was inherently faster than that for the solid/liquid interface using an electrolyte solution, while the interfacial resistance is usually high because the joint interface is imperfect. In addition, Si-Sn composites on LLZT were studied systematically to enable charging and discharging of thick electrodes. The charge/discharge cycle performance of 0.1 μm-thick Si-Sn thin-film electrodes was simply dependent on the Si:Sn composition ratio. On the other hand, the thicker electrodes with a thickness of 1 μm delivered the superior charge/discharge performance at a specific Si:Sn atomic ratio of 7:3. The Si7-Sn3 composite electrode had a distinctive nanostructure to facilitate the charge/discharge reactions of Si and to achieve the stable interface contact with LLZT.