Construction of sticky ionic conductive buffer layer for inorganic electrolyte toward stable all-solid-state lithium metal batteries

Abstract Inorganic electrolyte based all-solid-state lithium metal batteries (LMBs) are considered the most promising secondary power storage device. However, there still exist significant interfacial issues, which hurdles its advancement in application seriously. Herein, we synthesize a sticky anion-immobilized oligomer ionic conductor (AIOC) to construct a buffer layer for inorganic electrolyte. The AIOC displays high ionic conductivity (2.21 × 10−5 S cm−1), large Li+ transference number (0.65) at 30 °C, which is beneficial to promote homogenous lithium deposition, moreover, it endows a wide electrochemical window of 4.3 V (vs. Li+/Li). Based on these merits, when AIOC serves as buffer layer for Li1.5Al0.5Ge1.5(PO4)3 (LAGP) electrolyte, the interfacial stability and compatibility between LAGP and lithium metal anode can be enhanced remarkably. Upon which, the interfacial resistance of lithium symmetrical cell can be declined sharply (5313 Ω→718 Ω). Enduring 100-h galvanostatic charge-discharge cycling test, the surficial morphologies and elemental constitutions of the lithium metal anode and LAGP electrolyte almost remain unchanged as before. As a result, a LiFePO4/Li all-solid-state cell with AIOC modified Li1.5Al0.5Ge1.5(PO4)3 electrolyte enables to achieve a reversible discharge capacity of 120.1 mAh g−1 at 0.5C with a notable capacity retention of 86.3% in 100 cycles at 50 °C.