Properties and working mechanism of Sn-doped Li0.33La0.56TiO3-based all-solid-state supercapacitor

All-solid-state supercapacitors (ASSS) are considered promising candidates to eliminate the safety issues of liquid-electrolyte-involved devices, while lithium lanthanum titanate perovskite compounds have been reported as suitable electrolytes due to their high chemical stability. However, the unsatisfactory ionic conductivity compared with liquid-electrolytes still hinders their applications in emerging requirements. Aiming to find the factors impacting the intrinsic capacitances of the lithium lanthanum titanate perovskite compounds when used in ASSS, a series of Li0.33La0.560.11Ti1-xSnxO3 (LLTS, represents vacancy) compounds with different Sn4+ concentrations (nominal x = 0-5 mol%) have been synthesized in this study. The as-prepared LLTS ceramic with the Sn4+ content of 0.1 mol% exhibited the highest ionic conductivity, while more Sn4+ reduced the ionic conductivity in the bulk pellets. The ionic conducting ability of the electrolyte determines the overall electrical performance of the assembled ASSBs, i.e., the better ionic conductivity of the LLTS leads to the higher capacitance of the devices. In addition, we have found the coexistence of electrical double-layer capacitance and dielectric polarization capacitance in the LLTS-based ASSS, which could provide the guidance in designing high-performance devices with similar configurations.