Molten Salt Driven Conversion Reaction Enabling Lithiophilic and Air-Stable Garnet Surface for Solid-State Lithium Batteries

摘要

Garnet-type electrolytes show great potential in application of solid-statelithium batteries due to their high ionic conductivity and wide electrochemicalwindow. However, the formation of surface Li2_CO_3 derived from air exposuretriggers uneven contact with Li-metal, leading to undesirable dendrite growthand performance deterioration. Herein, the Li_3PO_4 layer replacing Li_2CO_3 contaminantis built on garnet surface by taking molten NH4H2PO4 salt drivenconversion reaction. The high-flowability molten salt contributes to conformalformation of Li_3PO_4, realizing the air-stable garnet by preventing the re-attackof H_2O/CO_2 in air. Besides, the high work of adhesion for Li3PO4 on Li-metalalong with the transformation from Li_3PO_4 to Li_3P/Li_2O when contacting withmolten Li-metal enables a lithiophilic interlayer, leading to a seamlessLi/garnet contact with ultralow interfacial resistance of 13 Ω cm~2. Such ionconductingbut electron-insulating layer regulates the uniform distribution ofLi-flux, enabling a large critical current density of 1.2 mA cm~（?2）. Furthermore,the solid LiCoO_2/Li cell with the modified garnet delivers a discharge capacityof 130 mAh g?1 at 30℃, accompanied by a capacity retention of 81 after150 cycles. This study proposes a promising solution for improvement of airstability and interfacial compatibility of garnet using facile molten salt treatment.