Through the joint efforts of Chinese and foreign scientists, new breakthroughs have been made in research related to solid-state batteries. Recently, Wang Chunyang, a researcher at the Shenyang National Research Center for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, and an international team used in-situ transmission electron microscopy technology to reveal for the first time the cause of sudden short circuits in solid-state batteries at the nanoscale and proposed corresponding countermeasures. The research results were published in the Journal of the American Chemical Society on May 20.
Currently, mobile phones and electric vehicles rely on lithium batteries for power, but liquid lithium batteries pose certain safety risks. Researchers are developing safer "all-solid-state batteries" that replace liquid electrolytes with solid electrolytes and can also be paired with lithium metal negative electrodes with higher energy density. However, this revolutionary battery faces a fatal problem: the solid electrolyte will suddenly short circuit and fail.
Using in-situ transmission electron microscopy observations, researchers found that the electron pathways formed by the precipitation of lithium metal and interconnection induced by internal defects in the solid electrolyte (such as grain boundaries, pores, etc.) directly led to the short circuit of the solid-state battery. This process is divided into two stages: soft short circuit and hard short circuit. Soft short circuits originate from the precipitation and instantaneous interconnection of lithium metal at the nanoscale. At this time, the lithium metal grows along defects such as grain boundaries and holes like tree roots, forming an instantaneous conductive path, which is a soft short circuit. With the high frequency occurrence of soft short circuits and the increase of short-circuit current, the solid electrolyte eventually completely loses its insulation ability, causing an irreversible hard short circuit.
Based on these findings, the research team developed a "rigid and flexible" inorganic-organic composite solid electrolyte using a mechanically flexible and electronically insulating three-dimensional polymer network, which effectively inhibited the lithium metal precipitation and interconnection inside the solid electrolyte and the short-circuit failure induced by it.
This study provides a new understanding of the nanoscale failure mechanism of solid electrolytes by clarifying the soft short circuit-hard short circuit transformation mechanism of solid electrolytes and its intrinsic relationship with lithium plating kinetics, and provides a new theoretical basis for the development of new solid-state batteries.
