Lithium nitrate reservoir enabling substantial improvement in the cycle life of anode-free and lithium metal batteries

Abstract

Li metal batteries attract significant attention owing to their high energy densities; however, the growth of Li dendrites and high reactivities of Li metal with liquid electrolytes lead to performance degradation and safety problems. As a solid electrolyte interphase (SEI)-forming additive for use in addressing these problems, LiNO3 stabilizes lithium metal by forming a robust, stable SEI on the Li anode surface. However, the use of LiNO3 is limited owing to its low degree of dissociation within the electrolyte. In this study, we propose a LiNO3 reservoir (LNR) that can store and continuously release LiNO3 into the electrolyte during charge-discharge cycling, which enables the formation and maintenance of a stable SEI layer on the lithium metal anode. Due to uniform Li deposition/stripping and the suppression of dendritic Li growth in the presence of the LNR, the anode-free and lithium (20 μm)/LiNi0.8Co0.1Mn0.1O2 cells with the LNR exhibit superior cycling performance compared to those of the cells without the LNR. The detailed mechanism of the substantial improvement in the cycling performance using the LNR is investigated using X-ray photoelectron spectroscopy, NMR spectroscopy, electrochemical impedance spectroscopy, and scanning electron microscopy.