Dendrite-free Li deposition using trace-amounts of water as an electrolyte additive. (July 2015)

• Record Type: Journal Article
• Authors: Qian, Jiangfeng; Xu, Wu; Bhattacharya, Priyanka; Engelhard, Mark; Henderson, Wesley A.; Zhang, Yaohui; Zhang, Ji-Guang
• Is Part Of: Nano energy. Volume 15(2015:Jul.)
• Page Start: 135
• Page End: 144
• Publication Date: 2015-07
• Subjects: Li deposition -- Dendrite-free -- Water additive -- LiF -- SEI layer; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2015.04.009
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: Residual water (H2 O) presents in nonaqueous electrolytes has been widely regarded as a detrimental factor for lithium (Li) batteries. This is because H2 O is highly reactive with the commonly used LiPF6 salt leading to the formation of HF which subsequently corrodes battery materials. In this work, we demonstrate that a controlled trace-amount of H2 O (25–50 ppm) can be an effective electrolyte additive for achieving dendrite-free Li metal deposition in LiPF6 -based electrolytes, while avoid detrimental effects. Detailed analyses revealed that the trace amount of HF derived from the decomposition reaction of LiPF6 with H2 O is electrochemically reduced during the initial Li deposition process to form a uniform and dense LiF-rich solid electrolyte interphase (SEI) layer on the surface of the substrate. This LiF-rich SEI layer leads to a uniform distribution of the electric field on the substrate surface thereby enabling uniform and dendrite-free Li deposition. Meanwhile, the detrimental effect of HF on the other cell components is diminished due to the consumption of the HF in the LiF formation process. Microscopic analysis reveals that the as-deposited, dendrite-free Li films exhibit a self-aligned and highly-compact Li nanorod structure which is consistent with a vivid blue color due to structural coloration. These findings clearly demonstrate a novel approach to control the nucleation and grow processes of Li metal films using a well-controlled, trace-amount of H2 O, as well as illuminate the effect of H2 O on other electrodeposition processes. Graphical abstract: Highlights: Dendrite-free Li film can be obtained with trace H2 O as electrolyte additive. The reactions from H2 O→HF→LiF-rich SEI layer occurred before Li deposition. H2 O and HF are consumed in the process so their detrimental effects are minimized. The dendrite-free Li film exhibits a highly aligned nanorod structure.