1. Introduction Light metal borohydrides, such as LiBH4, has a massive potential as hydrogen storage materials for storage applications in a wide scale. Most borohydridesrequire high temperatures for hydrogen release, but this can in many cases be lowered by utilizing eutectic composites, reactive hydride composites or by nanoconfinement. However, one major challenge still remains: Reversibility! In practically all metalborohydrides M-B12H12 species are formed during decomposition which ultimately reduces the reversible hydrogen storage capacity[1]. In order to understand or avoid this more knowledge of these compounds is required. Therefore this current study investigates Li2B12H12. Understanding Li2B12H12Bjarne R. S. Hansena andTorben R. Jensenaa Interdisciplinary Nano Science Center, Center for Materials Crystallography and Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark [1] In situ SR-PXD Sample preparation RT→ 700 °C (5K/min), p(H2) = vac. λ = 0.9941Å An in situ SR-PXD experiment on Li2B12H12 was performed at Maxlab, I711. At T = 280 °C a phase transformation is obser-ved, and at T = 355 °C the sample turns amor-phous and a broad hump is observed. Li2B12H12 - 4 H2O (Katchem) was heated to 240 °C under dynamic vacuum for 10 h to completely Li2B12H12 dry the sample and obtain an anhydrous, crystalline phase[2] β-Li2B12H12 γ-Li2B12H12-x The B12H122- ion [3] Thermal analysis As the temperature increases the hump is shifting towards lower 2θ angle. The end product is ex-pectedto be amorphous B. These observations agree well with thermal analysis and a previous study [4]. The fact that the sample becomes amor-phousduring heating complicates characteri-zationof the decomposition reactions with PXRD. Therefore 11B MAS NMR studies are currently being conducted. DSC and TGA indicatethreereaction steps arepresent, where the first step maybeowing to watercontamination. These steps willbefur-therinvestigatedusing FT-IR and 11B MAS NMR. Acknowledgements and references Sincereacknowledgementsare directed to the Interdisciplinary Nano Science Center (iNANO), Danscatt, MAX-Lab Bor4Store (EU) and Center for Materials Crystallography (CMC) [1] B. R. S. Hansen et al., J. Phys. Chem. C2013, 117, 7423−7432 [2] Pitt et al, J. Am. Chem. Soc.2013, 135, 6930−6941 [3] Whang et al., J. Phys. Chem. C, 2008, 112 (9), 3164–3169 [4] Paskevicious et al, Phys. Chem. Chem. Phys.2013, 15, 15825