Lithium Ion Disorder and Conduction Mechanism in LiCe(BH₄)₃Cl

Abstract

We investigate the diffusion mechanism of Li ions in LiCe(BH 4 ) 3 Cl, which exhibits fast Li ion conduction. It was previously shown that eight Li ions partially occupy the 12d Wyckoff sites in the I4̅ 3m structure and the Li ion diffusion takes place via jumping through the three-dimensional network of the 12d sites. In this study, we employ firstprinciples nudged elastic band simulation to elucidate the diffusion mechanism and discover that the Li ion does not directly jump to the neighboring 12d site, but instead passes through the closest 6b site. Moreover, the 6b site turns out to be another stable Li ion site, not just a transient point during a jump event. The occupation of the 6b site and the Li ion diffusion mechanism were assured by first-principles molecular dynamics simulations. The partial occupancy of the 12d site and 6b site at 500 K is approximately 1/2 and 1/3, respectively. The experimental diffraction data can be consistently interpreted. The peculiar crystal structure of LiCe(BH 4 ) 3 Cl allowing efficient and fast Li ion diffusion is again highlighted together with the role of [BH 4 ] − ion in thermodynamically stabilizing LiCe(BH 4 ) 3 Cl.

Investigation of the Reversible Lithiation of an Oxide Free Aluminum Anode by a LiBH4 Solid State Electrolyte

“…Recent interest in utilizing LiBH 4 as a solid-state electrolyte was established through the work of Orimo [4], who demonstrated that the ionic conductivity of lithium can be greater than 1 mS/cm at temperatures above the orthorhombic to hexagonal phase transition that occurs at 380 K [5]. This work has been expanded to achieve high conductivity in LiBH 4 based solid electrolytes through the addition of Li halide salts [6][7][8], nanoconfinement [9][10][11][12], nanoionic destabilization [13,14], ion substitution [15][16][17][18][19][20][21], and eutectic formation [22].…”

Beyond Typical Electrolytes for Energy Dense Batteries

“…Investigations of ionic conduction mechanisms in borohydrides showed that it is not only vacancy-dependent but also based on the "paddle-wheel" mechanism [47][48][49] wherein the high rotational mobility of the (M y X n ) δ− units promotes the ionic conductivity and lowers the activation energy [50,51]. This concept inspired investigating boron clusters (closo-borates)-based salts as electrolytes.…”

Electrolytes for Energy Dense Batteries

“…Investigations of ionic conduction mechanism in borohydrides showed that its not only vacancy-dependent but also based on the "paddle-wheel" mechanism. [47][48][49] wherein the high rotational mobility of the [MyXn] δ-units promotes the ionic conductivity and lowers the activation energy. [50][51] This concept inspired investigating boron clusters-based salts as electrolytes.…”