Garnet Electrolyte with an Ultralow Interfacial Resistance for Li-Metal Batteries

Abstract

Garnet-structured LiLaZrO is a promising solid Li-ion electrolyte for all-solid-state Li-metal batteries and Li-redox-flow batteries owing to its high Li-ion conductivity at room temperature and good electrochemical stability with Li metal. However, there are still three major challenges unsolved: (1) the controversial electrochemical window of garnet, (2) the impractically large resistance at a garnet/electrode interface and the fast lithium-dendrite growth along the grain boundaries of the garnet pellet, and (3) the fast degradation during storage. We have found that these challenges are closely related to a thick LiCO layer and the Li-Al-O glass phase on the surface of garnet materials. Here we introduce a simple method to remove LiCO and the protons in the garnet framework by reacting garnet with carbon at 700 °C; moreover, the amount of the Li-Al-O glass phase with a low Li-ion conductivity in the grain boundary on the garnet surface was also reduced. The surface of the carbon-treated garnet pellets is free of LiCO and is wet by a metallic lithium anode, an organic electrolyte, and a solid composite cathode. The carbon post-treatment has reduced significantly the interfacial resistances to 28, 92 (at 65 °C), and 45 Ω cm at Li/garnet, garnet/LiFePO, and garnet/organic-liquid interfaces, respectively. A symmetric Li/garnet/Li, an all-solid-state Li/garnet/LiFePO, and a hybrid Li-S cell show small overpotentials, high Coulombic efficiencies, and stable cycling performance.

Nanostructured Metal–Organic Framework (MOF)‐Derived Solid Electrolytes Realizing Fast Lithium Ion Transportation Kinetics in Solid‐State Batteries

“…Here, R 1 can be attributed to the resistance of the SE and cathode, and then R 2 can be ascribed to the resistances at the electrode/SE interfaces, since its characteristic capacitance is ≈10 −7 F. The initial internal resistance of the battery ( R 1 + R 2 ) at 60 °C is about 320 Ω, which is the lowest among the resistances of the batteries with different cathode compositions (Figure S9a, Supporting Information), and after subtracting the resistance of the Li/SE interface, the interfacial resistance at the LiFePO 4 /SE interface is determined to be about 206 Ω cm 2 (the area of the composite cathode is 0.785 cm 2 ). Hu and co‐workers reported an internal resistance of 6000 Ω cm 2 for the oxide‐based solid‐state lithium battery at 60 °C, even though the resistance at the cathode/oxide SE interface can be decreased to ≈92 Ω cm 2 at 65 °C with the aid of polymer . The low resistances of the Li/SE and LiFePO 4 /SE interfaces ensure the fast lithium‐ion transportation kinetics in the solid‐state lithium batteries using the nanostructured MOF–derived SEs.…”

Electrolytes for Rechargeable Lithium–Air Batteries

“…In general, surface polishing processes such as dry polishing using sandpaper, wet polishing using an automated polisher with polishing fluid, and heat treatment are used to remove the Li 2 CO 3 from Li 7 La 3 Zr 2 O 12 (LLZO) . Recently, Goodenough and co‐workers proposed a carbon post‐treatment to remove the Li 2 CO 3 and protons and decrease the amount of Li‐Al‐O glass phase in the garnet . Moreover, when the battery was deeply discharged, the consumed Li metal left gaps between the Li metal and solid electrolyte.…”

A Novel Aqueous‐based Gelcasting Process to Fabricate Li6.4La3Zr1.4Ta0.6O12 Solid Electrolytes

“…[1][2][3][4] However, the practical application of LLZO-based all-solid-state lithium metal batteries have been severely hindered by the high area specific resistance (ASR), which is attributed to the high bulk impedance of LLZO and interfacial impedance between LLZO electrolytes and electrodes . [1][2][3][4] However, the practical application of LLZO-based all-solid-state lithium metal batteries have been severely hindered by the high area specific resistance (ASR), which is attributed to the high bulk impedance of LLZO and interfacial impedance between LLZO electrolytes and electrodes .…”