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Commercial Li-ion batteries are vital to our daily lives, powering everything from portable devices to high-powered electric vehicles. The current usage of flammable liquid electrolytes in conventional Li-ion batteries creates risks, necessitating the development of solid electrolytes that are secure and reliable. However, the ionic conductivity of solid electrolytes cannot compete with liquid electrolytes. Herein, we report the synthesis of Li1·5Al0·3Si0·2Ti1·7P2·8O12 (LASTP) powder with improved ionic conductivity and evaluate its performance as a solid electrolyte in an all-solid-state battery (ASSB). A facile solution-based method is used for the LASTP synthesis with optimized sintering and calcination temperatures. As a result, the LASTP sintered at 1050 °C has the highest relative density (96.84%) and ionic conductivity (9.455 × 10−4 S/cm) with the lowest activation energy (Ea, 0.226 eV). A coin cell is assembled with Li/LASTP/Li(Ni0·65Co0·15Mn0.20)O2 all-solid-state configuration to evaluate the electrochemical performance. In addition, an electrospun polymer conductor film (PVDF-HFP) is added between the electrodes and the solid electrolyte to reduce the interfacial resistance. The ASSB has shown a stable and high performance with remarkable discharge capacity (205.3 mAh/g) at 0.1C and could be operated even after 100 cycles with 85.3% of retention at 0.2C. Therefore, the present work suggests that the LASTP solid electrolyte is a promising material for next-generation safe ASSBs.

Commercial lithium-ion batteries using liquid electrolytes are still a safety hazard due to their poor chemical stability and other severe problems, such as electrolyte leakage and low thermal stability. To mitigate these critical issues, solid electrolytes are introduced. However, solid electrolytes have low ionic conductivity and inferior power density. This study reports the optimization of the synthesis of sodium superionic conductor-type Li1.5Al0.3Si0.2Ti1.7P2.8O12 (LASTP) solid electrolyte. The as-prepared powder was calcined at 650 °C, 700 °C, 750 °C, and 800 °C to optimize the synthesis conditions and yield high-quality LASTP powders. Later, LASTP was sintered at 950 °C, 1000 °C, 1050 °C, and 1100 °C to study the dependence of the relative density and ionic conductivity on the sintering temperature. Morphological changes were analyzed using field-emission scanning electron microscopy (FE-SEM), and structural changes were characterized using X-ray diffraction (XRD). Further, the ionic conductivity was measured using electrochemical impedance spectroscopy (EIS). Sintering at 1050 °C resulted in a high relative density and the highest ionic conductivity (9.455 × 10−4 S cm−1). These findings corroborate with the activation energies that are calculated using the Arrhenius plot. Therefore, the as-synthesized superionic LASTP solid electrolytes can be used to design high-performance and safe all-solid-state batteries.