# Synthesis and Characterization of Li4(OH)3Br for Thermal Energy Storage

## TL;DR

This paper clarifies the thermal properties of Li4(OH)3Br, showing it has a lower but still useful energy storage capacity around 300°C.

## Contribution

The paper identifies the correct crystal structure of Li4(OH)3Br and corrects prior overestimations of its thermal storage capacity.

## Key findings

- The previously reported high melting enthalpy of Li4(OH)3Br was based on a metastable hydrated phase.
- The thermodynamically stable phase of Li4(OH)3Br has a melting enthalpy of 263 ± 3 J g–1 at ∼290°C.
- Theoretical modeling aligns with experimental results, confirming the corrected thermal properties.

## Abstract

The peritectic compound Li4(OH)3Br has been
suggested as a candidate material for latent heat thermal energy storage
(TES), due to its high calculated melting enthalpy (804 J g–1) around 300 °C, however experimental reports have obtained
much lower values (≤250 J g–1). In this work,
we show that the crystal structure established for Li4(OH)3Br in literature corresponds to a metastable hydrated compound,
and instead propose that the thermodynamically stable phase belongs
to the Pmnm space group. The hydrated phase dehydrates
at ∼175 °C, rendering the exceptional previous predictions
inapplicable. An experimentally measured melting enthalpy of 263 ±
3 J g–1 is found for high-purity Li4(OH)3Br. Theoretical modeling is used to suggest a crystal structure
for Li4(OH)3Br, from which a melting enthalpy
of 260 J g–1 is calculated, in good agreement with
the experimental work, and supporting that nonetheless impressive
storage capacity at ∼290 °C can be offered by Li4(OH)3Br.