High-temperature Li3(OH)2BR Phase

Building on previous work, a team made up of Oxford Materials, Newcastle Chemistry and Oxford Chemistry (led by this department), set out to explore characterising a phase with stoichiometry Li₃(OH)₂Br existing between ~225 and ~275 ^oC in the LiBr-LiOH phase diagram.  

Their paper 'Filling the gaps in the LiBr-LiOH phase diagram: a study on the high-temperature Li3(OH)2Br phase' published in Chemistry of Materials discusses how diffraction studies indicate that the phase takes a hexagonal unit cell, and that theoretical modelling is used to suggest a possible crystal structure.  Nuclear magnetic resonance spectroscopy and electrochemical impedance-spectroscopy measurements demonstrate excellent lithium-ion dynamics in this phase, with an ionic conductivity of 0.12 S cm ^-1 at 250 ^oC. 

The authors explain how initial attempts to stabilise the phase at room temperature through quenching were not successful, however, a metastable state demonstrating poor ionic conductivity was found to form.  This is an important consideration for the synthesis of Li₂OHBr solid-state electrolytes (also found in the LiBr-LiOH phase diagram) which are synthesised by cooling through phase fields containing Li₃(OH)₂Br and are therefore susceptible to these impurities.