Three-Dimensional, Solid-State Mixed Electron–Ion Conductive Framework for Lithium Metal Anode

Abstract

Solid-state electrolytes (SSEs) have been widely considered as enabling materials for the practical application of lithium metal anodes. However, many problems inhibit the widespread application of solid state batteries, including the growth of lithium dendrites, high interfacial resistance, and the inability to operate at high current density. In this study, we report a three-dimensional (3D) mixed electron/ion conducting framework (3D-MCF) based on a porous-dense-porous trilayer garnet electrolyte structure created via tape casting to facilitate the use of a 3D solid state lithium metal anode. The 3D-MCF was achieved by a conformal coating of carbon nanotubes (CNTs) on the porous garnet structure, creating a composite mixed electron/ion conductor that acts as a 3D host for the lithium metal. The lithium metal was introduced into the 3D-MCF via slow electrochemical deposition, forming a 3D lithium metal anode. The slow lithiation leads to improved contact between the lithium metal anode and garnet electrolyte, resulting in a low resistance of 25 Ω cm. Additionally, due to the continuous CNT coating and its seamless contact with the garnet we observed highly uniform lithium deposition behavior in the porous garnet structure. With the same local current density, the high surface area of the porous garnet framework leads to a higher overall areal current density for stable lithium deposition. An elevated current density of 1 mA/cm based on the geometric area of the cell was demonstrated for continuous lithium cycling in symmetric lithium cells. For battery operation of the trilayer structure, the lithium can be cycled between the 3D-MCF on one side and the cathode infused into the porous structure on the opposite side. The 3D-MCF created by the porous garnet structure and conformal CNT coating provides a promising direction toward new designs in solid-state lithium metal batteries.

Thick Electrode Batteries: Principles, Opportunities, and Challenges

“…To prepare the 3D SSEs, two types of garnet taps with different constituents have been used and stacked together, followed by a cosintering process to form the integrated bilayer structure after removing the organic binders and polymers. By changing the laminated structure or laminated layering of the garnet taps, tri‐layer SSEs with a porous/dense/porous architecture and diverse thicknesses are also achieved . Based on these 3D SSEs, diverse Li‐metal electrodes or Li‐metal batteries with high active material loading and improved energy density have been further reported .…”

The Effects of Constriction Factor and Geometric Tortuosity on Li‐Ion Transport in Porous Solid‐State Li‐Ion Electrolytes

“…This is especially true if the typical planar electrolyte is replaced by a more complex porous‐dense‐porous geometry such as employed by Hitz et al, which carries the potential to both improve solid‐state battery performance and magnify the effects of electrolyte microstructural limitations 35. Thus far, the results for full cells employing Li 6.75 La 2.75 Ca 0.25 Zr 1.5 Nb 0.5 O 12 (LLCZN) “trilayers” and similar bilayers were highly promising, showing lower area‐specific resistances while achieving higher electrode loading than planar electrolyte structures 36–38. This suggests that in these particular configurations, the potential structural limitations of the porous LLCZN layers did not pose a significant issue.…”

Controlling Li Ion Flux through Materials Innovation for Dendrite‐Free Lithium Metal Anodes

“…f) Li deposition/dissolution in 3D garnet framework with one side coated with CNTs. Reproduced with permission . Copyright 2018, American Chemical Society.…”