Tailoring of Li/LATP-PEO Interface via a Functional Organic Layer for High-Performance Solid Lithium Metal Batteries

Surface functionalization is an effective strategy to reduce the chemical reactivity between a Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) electrolyte and Li metal anode and optimize the interfacial contact of different components. Herein, sodium itaconate (SI) is introduced to modify the surfaces of LATP particles (LATP@SI) via a self-polymerizing process, and a composite solid electrolyte (CSE) composed of poly(ethylene oxide) (PEO) and LATP@SI is fabricated. Benefiting from the protection of the SI nanolayer, LATP demonstrates chemical compatibility with the Li metal anode, while the reduced surface energy renders a good dispersion of LATP in PEO. Furthermore, abundant carboxyl groups in SI can offer a bridge between LATP and PEO to accelerate Li⁺ transmission. As a result, the as-prepared PEO-LATP@SI-6 CSE exhibits a high ionic conductivity of 1.15 × 10^-4 S cm^-1 at 30 °C and 1.20 × 10^-3 S cm^-1 at 60 °C, a wide electrochemical stable window beyond 5.0 V, an improved Li⁺ transference number of 0.41, and an optimized lithium compatibility over 1200 h with Li dendrite free. The as-assembled Li||PEO-LATP@SI-6 CSE||LiFePO₄ full battery delivers a high reversible capacity of 155 mAh g^-1 and an outstanding capacity retention of 89% after 200 cycles. The Li||LiFePO₄ pouch cell also successfully runs 50 cycles with a terminal discharge capacity of 116.6 mA h g^-1. This study opens a new avenue to protect LATP. The developed surface functionalization technique promises a facile and efficient method for interfacial engineering to accelerate the practical application of LATP in solid-state lithium batteries.