Internal-External Dual-Modification Strategy for Enhancing Interfacial Stability and Ionic Transport in LATP-Based Solid-State Electrolytes

Abstract

The NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP) is a potential solid electrolyte, favored for its high ionic conductivity, excellent air stability and low cost. However, direct contact between LATP and lithium induces Ti4+ reduction to Ti3+, causing mechanical stress and structural degradation at both the interface and within the LATP structure, which severely limits solid-state battery applications. Here, we propose a novel internal-external dual-modification strategy to simultaneously optimize the bulk structure and interfacial stability of LATP-based solid-state electrolytes. Internally, ultra-fast joule heating sintering densifies LATP, reduces grain boundary resistance, and enhances lithium-ion transport. Externally, an in situ crosslinked polyethylene glycol diacrylate-based gel polymer electrolyte (PGPE) serves as an interfacial buffer layer, providing ionic conductivity, electronic insulation, and stress buffering. This hierarchical design enables the formation of a PGPE@P-LATP-J composite electrolyte exhibits a wide electrochemical window (4.91 V), high ionic conductivity (1.14 × 10⁻3 S·cm⁻1), and a lithium-ion transference number of 0.79. The modified LATP-based solid-state LiFePO4 (LFP) cells achieve 99.1% capacity retention after 200 cycles at 1 C, and the Li/Li symmetric cells maintain stable cycling over 1500 hours at 0.5 mA·cm⁻2. This work offers a practical strategy to address interfacial degradation in LATP-based systems and promotes the development of high-performance solid-state lithium batteries.