Chemical and electrochemical failure processes in the interface reaction between LATP and lithium metal anode

As a solid-state electrolyte suitable for all-solid-state Li metal batteries, Al-doped LiTi 2 (PO 4 ) 3 (LATP) exhibits high ionic conductivity, air stability, and low cost; however, it is subject to significant interface reactions with the Li anode. Herein, we demonstrate that the interface reaction of LATP with Li anode can be categorized into two distinct processes: a chemical reaction and an electrochemical reaction. Although the products of both reactions are Li 3 PO 4 , AlPO 4 , and Li 3 Ti 2 (PO 4 ) 3 , the chemical reaction occurs spontaneously between LATP and Li anode at the interface. The electrochemical reaction involves lithium ions and electron carriers being injected into LATP under applied voltage conditions, which then reacts with LATP within LATP. Such electrochemical reactions can lead to the fragmentation of LATP, resulting in a significant decrease in its ion transport capacity, which is primarily responsible for the failure of LATP-based lithium metal batteries. Notably, we found that LATP, traditionally regarded as an electronic insulator, demonstrates a certain electron transport capability under a specific voltage, which is a prerequisite for the occurrence of electrochemical reactions. Furthermore, we discovered that this electrochemical reaction can inhibit the growth of lithium dendrites in LATP