Hybrid Thin-Film Encapsulation for All-Solid-State Thin-Film Batteries

All-solid-state thin-film batteries have been actively investigated as a power source for various microdevices. However, insufficient research has been conducted on thin-film encapsulation, which is an essential element of these batteries as solid electrolytes and Li anodes are vulnerable to moisture in the atmosphere. In this study, a hybrid thin-film encapsulation structure of hybrid SiO_y/SiN_xO_y/a-SiN_x:H/Parylene is suggested and investigated. The water-vapor transmission rate of hybrid thin-film encapsulation is estimated to be 4.9 × 10^–3 g m^–2·day^–1, a value that is applicable to batteries as well as flexible solar cells, thin-film transistor liquid-crystal display, and E-papers. As a result of hybrid thin-film encapsulation, it is confirmed that the all-solid-state thin-film batteries are stable even after 100 charge/discharge cycles in the air atmosphere for 30 days and present a Coulombic efficiency of 99.8% even after 100 cycles in the air atmosphere. These results demonstrate that the thin-film encapsulation structure of hybrid SiO_y/SiN_xO_y/a-SiN_x:H/Parylene can be employed in thin-film batteries while retaining long-term stability.