Platinum nano-interlayer enhanced interface for stable all-solid-state batteries observed via cryo-transmission electron microscopy

Abstract

The unstable and inferior lithium/solid polymer electrolyte (Li/SPE) interface is a key challenge in the application of all-solid-state Li metal batteries (ASSLMBs). Moreover, the atomic-scale visualization of the Li/SPE interface in ASSLMBs has still not been achieved due to the difficulty in characterizing air and electron beam sensitive materials in normal microscopy. In addition, finding an efficient method to improve the Li/SPE interface is challenging. Here, we image the Li/poly(ethylene oxide) (PEO) interface using cryo-transmission electron microscopy (cryo-TEM). A mosaic Li/PEO interface consisting of inorganic-rich Li-containing phases (LiOH, Li₂O, Li, etc.) and organic components was atomically resolved. To improve the stability of the Li/PEO interface, a platinum (Pt) nano-interlayer was introduced between the SPE and Li metal to in situ form a conductive Li–Pt alloy. Such a functional alloy interlayer increased ion/electron conductivity, inhibited side reactions and promoted dense Li deposition. This effective strategy of modifying the interface resulted in a longer lifespan of the Li–Li half-cell, which exceeded 2000 h, and higher capacity retention over 98% after 270 cycles for the Li–LiFePO₄ full-cell, indicating that nanoscale interface modification is a promising strategy for achieving stable all-solid-state batteries.