PNNL

Abstract

This paper reports development of a lithium-ion battery nanostructure device using a single nanowire for in-stu TEM study of the battery. This prototype lithium ion battery was built using a single SnO2 nanowire as the anode, an air stable salt: lithium bis(trifluoromethansulfonyl) imide (LiTFSI) in a hydrophobic ionic liquid: 1-butyl-1-methylpyrrolidium TFSI (P14TFSI) as the electrolyte, and LiCoO2 as the cathode. The microstructure evolution of the single nanowire anode was studied using TEM imaging, electron diffraction, and electron energy-loss spectroscopy during the operation of the battery. It has been observed that during initial charging, the electrolyte was found to decompose and subsequently be electrodeposited on the anode, leading to the formation of a coating layer on the anode. This coating layer was enriched with Li. Formation of this layer will retard the Li intercalation of SnO2. This in situ TEM observation provides direct evidence that accounts for the observed low capacity and fast fading of the Li battery when LiTFSI-P14TFSI is used as the electrolyte.