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.

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.

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