High Li+ and Na+ Conductivity in New Hybrid Solid Electrolytes based on the Porous MIL-121 Metal Organic Framework

Roman Zettl, Sarah Lunghammer, Bernhard Gadermaier, Athmane Boulaoued, Patrik Johansson, H. Martin R. Wilkening*, Ilie Hanzu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Solid-state electrolytes (SSEs) can leapfrog the development of all-solid-state batteries (ASSBs), enabling them to power electric vehicles and to store renewable energy from intermittent sources. Here, a new hybrid Li+ and Na+ conducting SSE based on the MIL-121 metal-organic framework (MOF) structure is reported. Following synthesis and activation of the MOF, the free carboxylic units along the 1D pores are functionalized with Li+ or Na+ ions by ion exchange. Ion dynamics are investigated by broadband impedance spectroscopy and by 7Li and 23Na NMR spin-lattice relaxation. A crossover at 50 °C (Li+) and at 10 °C (Na+) from correlated to almost uncorrelated motion at higher temperature is observed, which is in line with Ngai's coupling model. Alternatively, in accordance to the jump relaxation model of Funke, at low temperature only a fraction of the jump processes are successful as lattice rearrangement in the direct vicinity of Li+ (Na+) is slow. 1H NMR unambiguously shows that Li+ is the main charge carrier. Conductivities reach 0.1 mS cm−1 (298 K, Na+) while the activation energies are 0.28 eV (Li+) and 0.36 eV (Na+). The findings pave the way towards development of easily tunable and rationally adjustable high-performance MOF-based hybrid SSEs for ASSBs.

Original languageEnglish
Article number2003542
JournalAdvanced Energy Materials
Volume11
Issue number16
DOIs
Publication statusPublished - 2021

Keywords

  • conductivity spectroscopy
  • ion dynamics
  • lithium ion conductors
  • metal–organic frameworks
  • sodium ion conductors
  • solid-state batteries

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

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