In situ observation of solid electrolyte interphase evolution in a lithium metal battery

Abstract

Lithium metal is a favorable anode material in all-solid Li-polymer batteries because of its high energy density. However, dendrite formation on lithium metal causes safety concerns. Here we obtain images of the Li-metal anode surface during cycling using in situ scanning electron microscopy. Constructing videos from the images enables us to monitor the failure mechanism of the battery. Our results show the formation of dendrites on the edge of the anode and isles of decomposed lithium bis(trifluoromethanesulfonyl)imide on the grain boundaries. Cycling at high rates results in the opening of the grain boundaries and depletion of lithium in the vicinity of the isles. We also observe changes in the surface morphology of the polymer close to the anode edge. Extrusion of lithium from these regions could be evidence of polymer reduction due to a local increase in temperature and thermal runaway assisting in dendrite formation.

Direct observation of lithium metal dendrites with ceramic solid electrolyte

“…Figure 2 depicts two dendrite morphologies of needle and mossy on the bottom Li electrode that were formed during Li deposition on the bottom side. These dendrites could have been initiated from the defects such as the grain boundaries, regions covered with thin solid electrolyte interphase (SEI) layer, and possible contaminations 19 , 21 . The fact that these dendrites are observed in this specific region of the bottom Li electrode from the top view could be due to possible low pressure in this area that allows for further dendrite growth outwards the cell.…”

“…This thickness reduction was correlated to Li metal dissolution, which is more uniform compared to that in Li metal polymer batteries reported by Golozar et al 18 and Hovington et al 1 . In batteries that use polymer electrolytes, a more local dissolution starting from the grain boundaries is observed 19 . In the case of LLZO, however, the dissolution of Li was observed in larger areas; in some cases containing a few neighboring grains at different parts of the Li electrode.…”

“…To induce dendrite growth, the Li electrode facing the SEM electron beam, which is monitored during cycling, has a smaller area than the LLZO with area of 1.33 cm 2 that creates edge effect 17 . A copper spring was used as contact electrode and to apply pressure on the Li film to push it on the LLZO electrolyte and to make good contact between them 17 , 19 . The lower Li electrode has the same area as LLZO and rest on the flat aluminum sample holder, which acts as a contact electrode and push the lower Li electrode on the LLZO electrolyte.…”

Modification of Lithium Metal Anode and Solid-State Electrolyte Interface with a Gel Electrolyte

“…6) and VTF2 (Eq. 7): 28 = exp (− ( − 0 ) ) (VTF2) (7) where A is prefactor with units of S/cm, T is temperature in Kelvin, and T0 is the Vogel temperature, which is the glass transition temperature of an ideal glass. Fits of the data using least squares regression with equations VTF1 and VTF2 are shown in Fig.…”

“…[1][2][3] While lithium metal has the highest specific capacity (3860 mAh/g) and the lowest electrochemical potential (−3.04 V vs standard hydrogen electrode) in comparison to any other battery anode materials, its use in rechargeable cells has been hindered by formation of metal dendrites in liquid electrolyte systems that can penetrate commercial plastic separators and cause both safety concerns and performance decay in long-term cycling applications. [4][5][6] "Beyond Lithium-ion" chemistries such as all-solid-state, Lithium/Sulfur and Lithium/O2 batteries have received a great deal of interest over the past decade [6][7][8][9][10][11] due to their high theoretical energy densities, far exceeding those of commercial Lithium-ion cells.…”