Enhanced Room-Temperature Ionic Conductivity of NaCB11H12via High-Energy Mechanical Milling

Fabrizio Murgia, Matteo Brighi, Laura Piveteau, Claudia E. Avalos, Valerio Gulino, Marc C. Nierstenhöfer, Peter Ngene, Petra De Jongh, Radovan Černý

Research output: Contribution to journalArticlepeer-review

Abstract

The body-centered cubic (bcc) polymorph of NaCB11H12 has been stabilized at room temperature by high-energy mechanical milling. Temperature-dependent electrochemical impedance spectroscopy shows an optimum at 45-min milling time, leading to an rt conductivity of 4 mS cm-1. Mechanical milling suppresses an order-disorder phase transition in the investigated temperature range. Nevertheless, two main regimes can be identified, with two clearly distinct activation energies. Powder X-ray diffraction and 23Na solid-state NMR reveal two different Na+ environments, which are partially occupied, in the bcc polymorph. The increased number of available sodium sites w.r.t. ccp polymorph raises the configurational entropy of the bcc phase, contributing to a higher ionic conductivity. Mechanical treatment does not alter the oxidative stability of NaCB11H12. Electrochemical test on a symmetric cell (Na|NaCB11H12|Na) without control of the stack pressure provides a critical current density of 0.12 mA cm-2, able to fully charge/discharge a 120 mA h g-1 specific capacity positive electrode at the rate of C/2.

Original languageEnglish (US)
Pages (from-to)61346-61356
Number of pages11
JournalACS Applied Materials and Interfaces
Volume13
Issue number51
DOIs
StatePublished - Dec 29 2021

Keywords

  • NaCBH
  • Nasuperionic conductor
  • boron chemistry
  • hydroborate
  • mechanical milling
  • solid electrolyte

ASJC Scopus subject areas

  • Materials Science(all)

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