According to CCTV, Wang Chunyang, a researcher at the Shenyang National Research Center for Materials Science of the Institute of Metals of the Chinese Academy of Sciences, and an international team have recently made an important breakthrough, using in-situ transmission electron microscopy technology to reveal the soft-short-hard circuit transition mechanism in inorganic solid-state electrolytes and the lithium precipitation dynamics behind it at the nanoscale for the first time, and the research results were published in the Proceedings of the American Chemical Society on May 20.
Mobile phones and electric vehicles rely on lithium batteries for power, but liquid lithium batteries have safety hazards, and researchers are developing safer “all-solid-state batteries” that replace liquid electrolytes with solid electrolytes, and can also be paired with lithium metal anodes with higher energy density.
However, this revolutionary battery faces a fatal problem – the solid-state electrolyte can suddenly short circuit and fail.
In situ electron microscopy shows that the electronic pathway formed by lithium metal precipitation and interconnection induced by internal defects in the solid electrolyte (such as grain boundaries and holes) directly leads to the short circuit of solid-state batteries, which is divided into two stages: soft short circuit and hard short circuit.
The soft short circuit stems from the precipitation and instantaneous interconnection of lithium metal at the nanoscale, when the lithium metal grows along the grain boundaries, holes and other defects like tree roots, forming an instantaneous conductive pathway. Subsequently, with the occurrence of high frequency of soft short circuits and the increase of short-circuit current, solid-state electrolytes are like “trained” smart switches, gradually forming memory conductive channels, and finally completely losing their insulation ability, causing irreversible hard short circuits.
In this process, at the tiny cracks inside the solid-state battery, nanoscale lithium metal “corrodes” the material structure like mercury that seeps into the metal, causing brittle cracks to spread, causing the battery to completely collapse from temporary leakage (soft short circuit) to permanent short circuit (hard short circuit). Systematic studies of a variety of inorganic solid electrolytes have shown that this failure mechanism is common in NASICON and garnet inorganic solid electrolytes.
Based on these findings, the research team developed an inorganic/organic composite solid-state electrolyte using a three-dimensional electronically insulated and mechanically elastic polymer network, which effectively inhibited the lithium metal precipitation, interconnection and short-circuit failure induced by the solid electrolyte, and significantly improved its electrochemical stability.
This study provides a new understanding of the nanoscale failure mechanism of solid electrolytes and provides a theoretical basis for the development of new solid-state electrolytes by elucidating the soft-short-circuit-hard short-circuit transition mechanism of solid-state electrolytes and their intrinsic correlation with lithium precipitation kinetics.
