Synthesis and Properties of NASICON-type LATP and LAGP Solid Electrolytes.

Inorganic solid electrolytes play a critical role in all-solid-state Li batteries achieving high safety and high energy densities. The synthesis approaches for solid electrolytes are important for both fundamental research and practical applications. Li1+xAlxTi2-x(PO4)3 (LATP) and Li1+xAlxGe2-x(PO4)3 (LAGP) are two representative solid electrolytes with Na superionic conductor (NaSICON) structure. Here in, we reviewed LATP and LAGP solid electrolytes from the synthesis perspective, and correlated with their structure and conductive properties, also presented their electrochemical applications in batteries. Firstly, the solid-based and liquid-based synthetic methods of LATP and LAGP solid electrolytes and the key influencing factors are described. Secondly, the crystal structure and phase purity from different synthetic approaches will be introduced. Thirdly, the conductive mechanism and the composition effects and synthesis effects on conductivities of LATP and LAGP solid electrolytes will be compared. Fourthly, the electrochemical applications of these two solid electrolytes in full batteries will be discussed, including the roles as solid electrolytes, composite component in electrodes, and surface coating on electrodes. In the last section, a brief outlook is provided on the future development of NaSICON-type solid electrolytes for all-solid-state batteries.