Lithium Expulsion from the Solid-State Electrolyte Li_6.4La₃Zr_1.4Ta_0.6O₁₂ by Controlled Electron Injection in a SEM

Abstract

The garnet ionic conductor is one of the promising candidate electrolytes for all-solid-state secondary lithium batteries, thanks to its high lithium ion conductivity and good thermal and chemical stability. However, its microstructure is difficult to approach because it is very sensitive to the inquisitive electron beam. In this study based on a scanning electron microscope (SEM), we found that the electron beam expulses the lithium out of LiLaZrTaO (LLZTO), and the expulsed zone expands to where a stationary beam could extend and penetrate. The expulsion of metallic lithium was confirmed by its oxidation reaction after nitrogen inflow into the SEM. This phenomenon may provide us an effective probe to peer into the conductive nature of this electrolyte. A frame-scan scheme is employed to measure the expulsion rate by controllable and more uniform incidence of electrons. Lithium accumulation processes are continuously recorded and classified into four modes by fitting its growth behaviors into a dynamic equation that is mainly related to the initial ion concentration and ion migration rate in the electrolyte. These results open a novel possibility of using the SEM probe to gain dynamic information on ion migration and lithium metal growth in solid materials.

Unravelling the room-temperature atomic structure and growth kinetics of lithium metal

“…As one of the important candidates of the next generation solid electrolyte, Li 7 La 3 Zr 2 O 12 (LLZO) and its derivates have been widely investigated because of their relatively high ionic conductivity and good chemical stability against lithium metal anode 24 , 25 . It has been reported by different research groups that lithium metal could be grown from LLZO under the electron beam irradiation 26 , 27 . Here we employed our method on LLZO and our observations indicate lithium metal growth on LLZO could be an illusion.…”

New horizons for inorganic solid state ion conductors

“…[34][35][36] Interest in glasses has reignited recently due to observations of dendrite growth through grain boundaries in polycrystalline ion conductors such as LLZO. [37][38][39] A particularly important advance was reported by Hayashi in 2014, where an extremely high conductivity of 1.7 Â 10 À2 S cm À1 was reported for a Li 2 S-P 2 S 5 glass-ceramic phase. 40 By employing glasses, unavoidable local mechanical pressure during cycling in ASSBs may be better compensated, while protective interphases are necessary in order to stabilize anode and/or cathode contacts.…”

A Flexible Electron-blocking Interfacial Shield for Dendrite-free Solid Lithium Metal Batteries

“…Although the mechanisms for Li dendrite growth remain elusive, the electron attack to the garnet electrolytes has recently received increased scrutiny since high electronic conductivity of SSEs was reported as the cause for certain types of Li dendrites 29 . The electron attack to the garnet electrolytes was recently visualized by SEM 30 . The electron beam in the SEM irradiated on the Ta-doped LLZO (LLZTO) surface can expulse the Li out of the LLZTO to satisfy the neutrality.…”