High Current Cycling in a Superconcentrated Ionic Liquid Electrolyte to Promote Uniform Li Morphology and a Uniform LiF-Rich Solid Electrolyte Interphase

Kalani Periyapperuma, Elisabetta Arca, Steven Harvey, Thushan Pathirana, Chunmei Ban, Anthony Burrell, Cristina Pozo-Gonzalo, Patrick Howlett

Research output: Contribution to journalArticlepeer-review

21 Scopus Citations

Abstract

High-energy-density systems with fast charging rates and suppressed dendrite growth are critical for the implementation of efficient and safe next-generation advanced battery technologies such as those based on Li metal. However, there are few studies that investigate reliable cycling of Li metal electrodes under high-rate conditions. Here, by employing a superconcentrated ionic liquid (IL) electrolyte, we highlight the effect of Li salt concentration and applied current density on the resulting Li deposit morphology and solid electrolyte interphase (SEI) characteristics, demonstrating exceptional deposition/dissolution rates and efficiency in these systems. Operation at higher current densities enhanced the cycling efficiency, e.g., from 64 ± 3% at 1 mA cm-2 up to 96 ± 1% at 20 mA cm-2 (overpotential <±0.2 V), while resulting in lower electrode resistance and dendrite-free Li morphology. A maximum current density of 50 mA cm-2 resulted in 88 ± 3% cycling efficiency, displaying tolerance for high overpotentials at the Ni working electrode (0.5 V). X-ray photoelectron microscopy (XPS), time-of-flight secondary-ion mass spectroscopy (ToF-SIMS), and scanning electron microscopy (SEM) surface measurements revealed that the formation of a stable SEI, rich in LiF and deficient in organic carbon species, coupled with nondendritic and compact Li morphologies enabled enhanced cycling efficiency at higher currents. Reduced dendrite formation at high current is further highlighted by the use of a highly porous separator in coin cell cycling (1 mAh cm-2 at 50 °C), sustaining 500 cycles at 10 mA cm-2.

Original languageAmerican English
Pages (from-to)42236-42247
Number of pages12
JournalACS Applied Materials and Interfaces
Volume12
Issue number37
DOIs
StatePublished - 16 Sep 2020

Bibliographical note

Publisher Copyright:
Copyright © 2020 American Chemical Society.

NREL Publication Number

  • NREL/JA-5K00-77342

Keywords

  • high current
  • high efficiency
  • ionic liquid
  • LiF
  • SEI
  • superconcentrated

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