Polymorphism, ionic conductivity and electrochemical properties of lithium closo-deca- and dodeca-borates and their composites, Li2B10H10–Li2B12H12

DOI: 10.1039/D2TA00337F

Authors: Chongyang Zhou (Aarhus University; Wuhan University of Technology) , Jakob B. Grinderslev (Aarhus University) , Lasse N. Skov (Aarhus University) , Mathias Jorgensen (Aarhus University) , Yuanzhi Li (Wuhan University of Technology) , Jørgen Skibsted (Aarhus University) , Yigang Yan (Sichuan University) , Torben R. Jensen (Aarhus University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Materials Chemistry A , VOL 1

State: Published (Approved)
Published: July 2022

Abstract: Metal closo-borates are attractive electrolytes for solid state batteries. Here we present a detailed investigation of the polymorphism and thermal and electrochemical properties of Li2B10H10 and Li2B12H12 and their composites, (1 − x)Li2B12H12–xLi2B10H10. A new polymorph, β-Li2B10H10, is identified with a cubic structure, a = 9.567(1) Å (Fm[3 with combining macron]m), with dynamically disordered B10H102− anions. A sub-stoichiometric compound denoted as γ-Li2B10H10−y is prepared by thermal treatment (380 °C, 1 hour) in hydrogen and can be indexed to a cubic face-centered unit cell with a = 9.9224(5) Å. The 7Li MAS NMR spectra along with spin–lattice relaxation (T1) measured by 7Li saturation-recovery NMR experiments clearly reveal a high degree of dynamics assigned to increasing amounts of γ-Li2B10H10−y, which is in accordance with the measured Li+ ionic conductivity. Thermal treatment (380 °C, 1 hour) of Li2B12H12 in argon reveals the highest degree of dynamics and Li+ conductivity. The (1 − x)Li2B12H12–xLi2B10H10 composites are found to be physical mixtures of γ-Li2B10H10−y and Li2B12H12 with minor amounts of α-Li2B10H10, and their Li+ conductivities are proportional to the amount of γ-Li2B10H10−y. The highest Li+ conductivity is observed for γ-Li2B10H10−y: σ(Li+) = 7.6 × 10−6 S cm−1 at 30 °C and 7.2 × 10−3 S cm−1 at T = 330 °C. Cyclic voltammetry of γ-Li2B10H10−y reveals an oxidative stability up to 2.8 V vs. Li/Li+, and a stable plating and stripping of lithium.

Diamond Keywords: Batteries; Solid-State Batteries (SSB)

Subject Areas: Materials, Chemistry, Energy


Instruments: I11-High Resolution Powder Diffraction

Added On: 21/07/2022 09:25

Discipline Tags:

Energy Storage Energy Physical Chemistry Energy Materials Chemistry Materials Science

Technical Tags:

Diffraction X-ray Powder Diffraction