Significant Reduction in the Interfacial Resistance of Garnet-Type Solid Electrolyte and Lithium Metal by a Thick Amorphous Lithium Silicate Layer

The poor ionic and electronic contacts between electrodes and the electrolyte is a critical problem in the fabrication of all-solid-state lithium batteries based on garnet-type oxide solid electrolytes. The interfacial resistance with lithium metal anode has been widely studied because the use of lithium metal anodes can provide energy storage systems with the largest specific energy. Here, an amorphous lithium silicate interlayer is proposed to obtain a low interfacial resistance of the garnet solid electrolyte with lithium metal. The lithium silicate layer is deposited on the garnet solid electrolyte by a liquid-phase process followed by heat treatment, and metallic lithium is put on the modified surface by just pressing, without heat treatment. This approach achieves a low interfacial resistance of 44 Ω cm2 and a stable dissolution/deposition cycling behavior at a current density of up to 0.5 mA cm–2. A quasi-solid-state battery constructed with the garnet solid electrolyte modified with the lithium silicate layer, lithium metal, and LiNi1/3Co1/3Mn1/3O2 electrode shows a stable cycling performance at 25 °C (124 mAh g–1 after 100 cycles). Thermodynamic calculations suggest that the effective contact between lithium metal and lithium silicate is created by the formation of Li–Si phases at the interface.