Stability and conductivity of cation- and anion-substituted LiBH4 -based solid-state electrolytes

Zhenpeng Yao, Soo Kim, Kyle Michel, Yongsheng Zhang, Muratahan Aykol, Chris Wolverton*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

The high-temperature phase of LiBH4 (HT-LiBH4) exhibits a promisingly high lithium ion conductivity but is unstable at room temperature. We use density functional theory (DFT) calculations to investigate the stabilization effect of halogen and alkali cation/anion substitutions on HT-LiBH4 as well the underlying mechanism for the high lithium ion conductivity. We find that increasing the substituent concentration enhances the stabilization of HT-LiBH4 (i.e., the DFT energy difference between the low- and high-temperature forms of substituted LiBH4 is reduced). Cation/anion substitution also leads to a higher Li defect (vacancy, interstitial, and Frenkel) formation energy, thereby reducing the Li defect (vacancy, interstitial, and Frenkel) concentrations. Using DFT migration barriers input into kinetic Monte Carlo simulations and the Materials INTerface (MINT) framework, we calculate the room-temperature lithium ion conductivities for Li(BH4)1-xIx (x=0.25 and 0.5) and Li1-yKyBH4 (y=0.25). Our calculations suggest that the lower I concentration leads to a higher lithium ion conductivity of 5.7×10-3 S/cm compared with that of Li(BH4)0.5I0.5 (4.2×10-5 S/cm) because of the formation of more Li-related defects. Based on our findings, we suggest that the stabilization of HT-LiBH4-based lithium ion conductors can be controlled by carefully tuning the cation/anion substituent concentrations to maximize the lithium ionic conductivities of the specific system.

Original languageEnglish (US)
Article number065402
JournalPhysical Review Materials
Volume2
Issue number6
DOIs
StatePublished - Jun 19 2018

Funding

Z.Y. and C.W. (DFT stability, defect formation energy, and conductivity) acknowledge supports from the Center for Electrochemical Energy Science (CEES), an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences under Award No. DEAC02-06CH11357. S.K. (initial defect calculations) was supported by the financial assistance Award No. 70NANB14H012 from U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design (CHiMaD). K.M. (KMC simulations) acknowledges the support from the US Department of Energy, Office of Science, Basic Energy Sciences, under Grant No. DEFG02-07ER46433. M.A. (structure analysis) was supported by the Dow Chemical Company. We gratefully acknowledge the computing resources from (1) the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported under Contract No. DE-AC02-05CH11231 and (2) Blues, a high-performance computing cluster operated by the Laboratory Computing Resource Center at Argonne National Laboratory.

ASJC Scopus subject areas

  • General Materials Science
  • Physics and Astronomy (miscellaneous)

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