부산대학교 도서관

Over the past few decades, Li-ion batteries (LIBs) have gained widespread adoption as essential components in energy storage devices and are the most important components for the large-scale energy applications of energy storage systems and electric vehicles. The safety concerns associated with LIBs are of significant importance owing to their utilization in extensive energy applications. Typical LIBs are based on liquid electrolytes, which is composed of a Li salt and flammable organic solvents, which can indeed lead to thermal instabilities and potentially result in explosions or fires. As a result of these long-standing safety issues, liquid electrolytes are being replaced by solid electrolytes, which are composed of non-flammable materials. Moreover, solid electrolytes offer advantages such as enhanced energy density and thermal stability.Recently, a Li-ion solid electrolyte material, LiTa2PO8 (LTPO), has been reported, which has a three-dimensional (3D) Li-ion conduction honeycomb-like pathway. The bulk ionic conductivity of LTPO is 1.6 × 10−3 S/cm and its total ionic conductivity is 2.5 × 10−4 S/cm at room temperature. However, it exhibits a limited the grain boundary ionic conductivity, which lowers its total ionic conductivity.Numerous studies have been carried out on solid-state electrolytes with the aim of enhancing their ionic conductivity. Among such studies, one common approach to enhance bulk ionic conductivity is by altering the crystalline structure of the electrolytes through the introduction of different ions via doping. However, these enhancements are constrained by the fact that it's the grain boundary, rather than the bulk, that predominantly influences the overall ionic conductivity. Consequently, improvement of the grain boundary ionic conductivity is a crucial and efficacious approach to augmenting the overall ionic conductivity of inorganic solid electrolytes. Generally, the sintering of ceramics demands elevating temperatures above 1000 °C. Whereas, the cold sintering process (CSP) was introduced, offering the capability to achieve densification in ceramics and composites at exceptionally low temperatures, below 300 °C. The attraction of the low sintering temperature lies in its suitability for fabricating ceramic-based solid electrolytes, as it mitigates the risk of Li evaporation. The CSP generates a kinematically limited amorphous or recrystallized phase, which is an intermediate phase that forms between particles, via a multistage non-equilibrium process involving the dissolution–precipitation of particle surfaces, and the evaporation of transient solvent, to prepare a saturated solution.In this study, to achieve the ionic conductivity comparable to LTPO ceramic electrolytes obtained via high-temperature sintering, the CSP conditions were modified to promote the formation of various species of amorphous layers at the LTPO particle interface. the effect of the interface layer at the LTPO particle interface on the microstructure and the electrochemical properties was investigated.In conclusion, we achieved the fabrication of LTPO solid electrolyte with various species of interface layers. This works provide evidence that the CSP is a promising alternative process to high-temperature sintering for the fabrication of ceramic-based solid electrolytes and introducing an amorphous layer at the particle interface in ceramic-based solid electrolytes is a solution to the issues associated with low grain boundary ionic conductivity.