Unveiling the Stable Nature of the Solid Electrolyte Interphase between Lithium Metal and LiPON via Cryogenic Electron Microscopy

Abstract

A combination of cryogenic electron microscopy and cryogenic focused ion beam enabled the characterization of the interface between Li metal and lithium phosphorous oxynitride, one of the well-known interfaces to exhibit exemplary electrochemical stability with a lithium metal anode. The probed structural and chemical information leads to a more comprehensive understanding of the underlying cause for the interfacial stability and its formation mechanism.

Suppressing void formation in all-solid-state batteries: the role of interfacial adhesion on alkali metal vacancy transport

“…Further development of experimental probes of the local structure, such as cryogenic electron microscopy (TEM), is required to understand how the phases formed during decomposition of SSE materials in contact with alkali metals are spatially distributed, as was recently shown for the LiPON system. 79 Previous computational models have indicated that the bonding between metals and highly ionic ceramics is typically weak, as the interfacial bonding is primarily electrostatic in nature. 80 This is consistent with the small W ad values observed for the LiCl, NaCl, NaBr and Li 2 O interfaces (Table S5).…”

Recent advancements in solid electrolytes integrated into all-solid-state 2D and 3D lithium-ion microbatteries

“…For instance, using electroanalytical measurements, cryogenic electron microscopy, and in situ electron microscopy, it was shown that LiPON forms a stable interface (up to 80 nm) with Li, reducing the Li loss during interface formation and further cycling compared to the liquid electrolytes, therefore providing a stable (de)intercalation of Li. [213][214][215] The composition of this layer with N and P concentration gradients and their unique spatial distribution acts as an effective passivation layer. [214][215][216] LiPON/LCO interface, its composition, and electronic structure have been also studied by such techniques as X-ray photoemission spectroscopy, scanning transmission electron microscopy (STEM) coupled with electron energy loss spectroscopy (EELS).…”

Interface Aspects in All‐Solid‐State Li‐Based Batteries Reviewed

“…The main motivation of using cryo‐EM is its ability to preserve Li metal and other battery components in their native state for quantitative analyses. [ 278,279 ] The mitigated beam damage allows higher dose and thus higher resolution images to be taken. It has been shown that the Li atoms in dendrites can sustain 30 s of exposure at 1000 e Å −2 s −1 without any changes on atomic resolution images.…”

“…It has been shown that the Li atoms in dendrites can sustain 30 s of exposure at 1000 e Å −2 s −1 without any changes on atomic resolution images. [ 280 ] New cryo‐FIB techniques are adopted to conserve fully intact interfaces during milling while other innovative ways of sample preparation (e.g., using redeposited Li [ 279 ] as the connection material instead of Pt) have been developed to further protect the reactive materials in their pristine state.…”

“…More recently, the Li/LiPON interface was preserved by cryo‐FIB and characterized by cryo‐EM techniques. [ 279 ] An interlayer of <80 nm thick was observed by cryo‐high‐resolution TEM which consists of a variety of crystalline decomposition products embedded in an amorphous matrix. The nature of these nanocrystals was further revealed by Cryo‐STEM–EELS to be Li 2 O, Li 3 N, and Li 3 PO 4 .…”