Direct observation of lithium metal dendrites with ceramic solid electrolyte

Abstract

Dendrite formation, which could cause a battery short circuit, occurs in batteries that contain lithium metal anodes. In order to suppress dendrite growth, the use of electrolytes with a high shear modulus is suggested as an ionic conductive separator in batteries. One promising candidate for this application is Li7La3Zr2O12 (LLZO) because it has excellent mechanical properties and chemical stability. In this work, in situ scanning electron microscopy (SEM) technique was employed to monitor the interface behavior between lithium metal and LLZO electrolyte during cycling with pressure. Using the obtained SEM images, videos were created that show the inhomogeneous dissolution and deposition of lithium, which induce dendrite growth. The energy dispersive spectroscopy analyses of dendrites indicate the presence of Li, C, and O elements. Moreover, the cross-section mapping comparison of the LLZO shows the inhomogeneous distribution of La, Zr, and C after cycling that was caused by lithium loss near the Li electrode and possible side reactions. This work demonstrates the morphological and chemical evolution that occurs during cycling in a symmetrical Li–Li cell that contains LLZO. Although the superior mechanical properties of LLZO make it an excellent electrolyte candidate for batteries, the further improvement of the electrochemical stabilization of the garnet–lithium metal interface is suggested.

In Situ and In Operando Techniques to Study Li-Ion and Solid-State Batteries: Micro to Atomic Level

“…Golozar et al [42] performed a chemical analysis of the cross-section of the Li-metal anode and the polymer electrolyte, showing the presence of salt in the vicinity of the isles formed on the anode and inhomogeneous salt distribution in the polymer, respectively. EDS mapping of symmetrical Li cells with LLZO electrolyte has also shown differences in the Li thickness on the anode, as well as the inhomogeneous distribution of Zr, La, and C in the cross-section of the electrolyte reported by Golozar et al [38].…”

“…Figure 1 shows the different dendrite morphologies reported using SEM. Golozar et al [38] also observed dendrites with mossy and needle morphologies in a symmetrical Li-metal cell with Li 7 La 3 Zr 2 O 12 (LLZO) electrolyte. This study showed the formation and growth of the dendrites on the Li electrode from regions that thinning of the anode and consumption of Li had occurred [38].…”

“…Golozar et al [38] also observed dendrites with mossy and needle morphologies in a symmetrical Li-metal cell with Li 7 La 3 Zr 2 O 12 (LLZO) electrolyte. This study showed the formation and growth of the dendrites on the Li electrode from regions that thinning of the anode and consumption of Li had occurred [38]. Kaboli et al [39] also reported mossy and needle dendrites in an all-solidstate battery with Li-metal anode, nickel-manganese-cobalt-oxide (NMC-622) cathode, and polymer electrolyte.…”

“…Milling the polymer electrolyte also showed the regions through which the dendrites perforated [15]. In situ SEM study of symmetrical Li cells with LLZO electrolyte conducted by Golozar et al [38] revealed the Li consumption mechanism during cycling. The images captured the inhomogeneous thinning of Li anode with different sizes from different regions, some of which contained a few grains.…”

“…Figure 4 shows the schematic of the surface and cross-section view assembly of the batteries as well as the setup used to study symmetrical Li cells with LLZO solid electrolyte [15,38].…”