Interface characteristics of Li1+xAlxTi2-x(PO4)3 solid electrolyte with Ta-doping for All-Solid-State batteries

Li1+xAlxTi2-x(PO4)3 (LATP) is a promising solid-state electrolyte, but it introduces stability issues because Ti reduces when it comes into contact with Li metal. Here, Ta doping was performed on the LATP electrolyte to confirm its influence on Ti reduction. Further, the crystal structure and ionic conductivity were analyzed to optimize the amount of Ta. We also used electron energy loss spectroscopy to visually demonstrate that Ta doping mitigated the reduction of Ti, which was confirmed by the presence of a mixed Ti4+/Ti3+ peak in the energy loss spectrum. Moreover, the applicability of Ta-doped LATP was confirmed in all-solid-state batteries, which showed a high coulombic efficiency and capacity of 98.6% and 0.072 mAh cm-2, respectively. These findings suggest a possible way to improve the chemical stability of LATP.