Synthesis and comprehensive thermophysical investigation of a novel organic-inorganic ion-coordinated cocrystal phase change material for medium-temperature thermal energy storage applications

Latent heat storage using phase change materials (PCMs) requires materials that combine sharp thermal transitions with structural robustness and long-term stability. This study reports the development of a novel organic–inorganic cocrystal PCM formed between m-Inositol and Lithium Nitrate at a binary composition of 72 wt% m-Inositol and 28 wt% LiNO 3 , establishing a new non-covalent derivative (NCD) designed for medium-temperature thermal energy storage. The synthesized cocrystal exhibits a sharp and congruent melting onset at 196 °C with a favourable melting enthalpy of 166.40 J/g, with no evidence of phase separation or metastability. A thermal decomposition onset near 300 °C provides a substantial safety margin of nearly 100 °C above the melting point, demonstrating excellent thermal robustness. Crystallographic characterization confirms the formation of a distinct, single-phase crystalline compound, as evidenced by the complete disappearance of the parent diffraction peaks and the appearance of new reflections. Microstrain analysis reveals lattice distortion and directional strain reversal, attributed to Li + –OH ion–dipole coordination within the inositol ring, which validates significant crystal rearrangements in the new phase. Microstructure imaging studies reveal a transformation from precursor morphologies to uniform polyhedral crystals, while the spectral analysis exhibits pronounced perturbations in the OH and NO 3 − vibrational bands, indicating strongly, nitrate integration and coordinated Li + interactions. Preliminary thermal cycling tests, conducted over 10 cycles, further confirm the material's short-term cycling stability. Collectively, these results establish this m-Inositol–LiNO 3 binary system as a thermally stable and structurally distinct ion-coordinated cocrystal PCM, offering strong potential for medium-temperature thermal energy storage applications and supporting advances aligned with UN SDGs 7, 9, 11, and 12. • Novel organic-inorganic ion-coordinated cocrystal PCM synthesized & characterized • Exhibits ΔH = 166.4 J/g, at a melting point of 196 °C with superior thermal stability • Ion-dipole interactions - key to the cocrystal's novel structure and stability • Promising potential for medium temperature (100–200 °C) storage applications