Negating interfacial impedance in garnet-based solid-state Li metal batteries

Abstract

Garnet-type solid-state electrolytes have attracted extensive attention due to their high ionic conductivity, approaching 1 mS cm, excellent environmental stability, and wide electrochemical stability window, from lithium metal to ∼6 V. However, to date, there has been little success in the development of high-performance solid-state batteries using these exceptional materials, the major challenge being the high solid-solid interfacial impedance between the garnet electrolyte and electrode materials. In this work, we effectively address the large interfacial impedance between a lithium metal anode and the garnet electrolyte using ultrathin aluminium oxide (AlO) by atomic layer deposition. LiLaCaZrNbO (LLCZN) is the garnet composition of choice in this work due to its reduced sintering temperature and increased lithium ion conductivity. A significant decrease of interfacial impedance, from 1,710 Ω cm to 1 Ω cm, was observed at room temperature, effectively negating the lithium metal/garnet interfacial impedance. Experimental and computational results reveal that the oxide coating enables wetting of metallic lithium in contact with the garnet electrolyte surface and the lithiated-alumina interface allows effective lithium ion transport between the lithium metal anode and garnet electrolyte. We also demonstrate a working cell with a lithium metal anode, garnet electrolyte and a high-voltage cathode by applying the newly developed interface chemistry.

Rechargeable Solid‐State Li–Air and Li–S Batteries: Materials, Construction, and Challenges

“…[134,136,137] Surprisingly, the surface coated with ultrathin Al 2 O 3 from atomic layer deposition (ALD) effectively negates the interfacial resistance from 1710 to 1 Ω cm 2 , as illustrated in Figure 17c and provides a stable voltage of 13 mV in Li plating and stripping plots (Figure 17d). [133] Schematic diagrams in Figure 17a also demonstrate that the Al 2 O 3 film wetting the solid electrolyte surface results in a compact interfacial contact, which is consistent with the SEM images in Figure 17b. First-principles computations suggest that the lithiated-alumina interface provides a facile Li ion transport between Li metal and solid electrolyte and wets the Li metal that is in contact with garnet electrolyte.…”

“…Thin film alloy prepared by magnetron sputtering, physical vapor deposition, or chemical vapor deposition have an outstanding capacity retention, which can be attributed to the strong adhesion of atoms onto the substrate support and elimination of the changing phase structure with different Li host. [126][127][128][129][130][131][132][133][134][135][136] However, Li-Al alloy mounds were present on the Al anode film surface instead of the Al-solid electrolyte surface, [126] and the cell capacity degraded as a result of Li trapping in these alloy mounds. This result indicates that only alloy film anodes seem inadequate for the solid-state Li metal battery.…”

Ion dynamics in solid electrolytes for lithium batteries

“…If high-voltage cathode materials are used to increase the power and energy density of the system, the electrolyte has to withstand potentials as a high as 5 V. Although electrochemical stability of solid electrolytes has been shown to be much better than that of liquid organic blends [84], the long-term stability of a given solid at high cathode potentials or being in contact with Li metal is still one of the white areas future research has to tackle. Placing a very thin, artificial interlayer such as crystalline (or amorphous) LiAlO 2 , LiTaO 3 , LiNbO 3 or even Al 2 O 3 [85] at the cathode-electrolyte interface may increase chemical and electrochemical stability [21,79,86,87]. These electronically insulating extra phases may, however, suffer from low intrinsic conductivity.…”

Review—Practical Challenges Hindering the Development of Solid State Li Ion Batteries

“…The advantage of energy density remains to be realized in solid state electrolytes (SSEs) since most studies to date utilize thick SSEs or cathodes with low active loading compared to liquid counterparts. 4,5 Furthermore, the desire to use SSEs in conjunction with Li metal anodes requires understanding and managing the morphology of Li metal plating, which can impact volumetric energy density. Operation at both higher and lower temperature compared to conventional technologies is a significant potential advantage of SSE systems.…”

“…75,181,182 At room temperature, nearly negligible interfacial impedances and 1 cm 2 have been shown for LPS|Li and LLZO|Li using best practices. 5,183 Oxide systems have been shown in true solid state architecture by either growing a thin cathode atop LLZO, 184,185 or using a low melting point conducting agent such as Li 3 BO 3 in the cathode. 186 A bulk co-sintering approach to create a bonded cathode-SSE interface introduces significant material compatibility issues during high temperature processing.…”