halvorhv

• Hval, Halvor Høen & Fjellvåg, Helmer (2025). Tracking phase transformations in LiMn1.5+xNi0.5−xO4 by high resolution X-ray diffraction. Journal of Materials Chemistry A. ISSN 2050-7488. 13, s. 41122–41143. doi: 10.1039/d5ta05130d. Fulltekst i vitenarkiv Vis sammendrag

  The stability and structural aspects of three categories of quenched and annealed LMNO samples, representing different stages in the processing of realistic materials, were studied by synchrotron powder X-ray diffraction and Raman spectroscopy. The complex Li–Mn–Ni–O energy landscape opens for coexistence of up to five phases under non-equilibrium conditions. These were evaluated by Rietveld refinements, assisted by lattice parameter – composition correlations, which quantitatively confirmed the nominal bulk composition. Mn/Ni cation diffusion occurs at much lower temperatures (400 °C) than previously anticipated, evidenced by Mn/Ni cation ordering in LMNO and by the (back-)formation of rock salt (o-RS) and N-layered impurity phases. Raman data reveals local Mn/Ni ordering well before the formation of domains detectable by X-ray diffraction. The formation of o-RS and Mn/Ni ordering occurs within the same temperature window. We find that o-RS is most likely the cause for oxygen release, without formation of O-vacancies in the parent spinel. A Mn-enriched e-LMNO spinel phase can form at low temperature alongside the ordering process and back-transformation of Ni-rich impurities. Such Mn/Ni segregations are the main cause of Mn(III) formation in LMNO electrodes. The described procedure provides a basis for detailed analysis of practical LMNO materials, emphasizing that the o-RS phase must be considered an integral part of all such analyses. Operando SXRD data further show that ordered and disordered LMNO can be distinguished during cycling, that tetragonal variants form at deep discharge, and that o-RS remains largely undetectable due to its small amount.

• Thøgersen, Rasmus Vester; Hval, Halvor Høen & Fjellvåg, Helmer (2024). Elucidation of the Reaction Mechanisms in Antifluorite-Type Li<inf>5+x</inf>Fe<inf>1-x</inf>Co<inf>x</inf>O<inf>4</inf> Positive Electrodes for Li-Ion Batteries. Batteries & Supercaps. doi: 10.1002/batt.202400348. Fulltekst i vitenarkiv Vis sammendrag

  The Li-rich antifluorite-type oxides Li5FeO4, Li5.5Fe0.5Co0.5O4 and Li6CoO4 have been investigated as positive electrode materials for Li-ion batteries in a combined operando XANES and XRD experiment. All materials show a similar two-step behaviour upon initial charge (termed Stage I and Stage II), and reversibility of subsequent cycling depends upon whether the initial charge cycle is terminated following Stage I or allowed to proceed through Stage II. By tracking the energetic evolution of the XANES pre-edge feature present in both Fe and Co K-edge spectra, as well as the evolution of X-ray diffractograms during charge and discharge, we correlate the changes in chemical coordination and oxidation states in both species and the structural changes to the electrochemical potential profile, and infer the role of anionic redox processes.

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• Skogvoll, Vidar; Garvang, Even Sletteng & Hval, Halvor Høen (2024). Under kappa - #25 - Green lantern - Batterier, farger, følelser og plancks konstant med halvor høen hval. [Radio]. Podcast. Fulltekst i vitenarkiv
• Lian, Torleif; Troøyen, Susanne Hansen; Forseth, Sissel; Raniseth, Amund Midtgard & Hval, Halvor Høen (2022). Safety of solid-state lithium-ion cell Thermal stability of LNMO and NMC materials. Fulltekst i vitenarkiv
• Hval, Halvor Høen (2020). Make Batteries Safe Again. Fulltekst i vitenarkiv
• Hval, Halvor Høen (2020). Om batterier og det å studere kjemi ved UiO. Fulltekst i vitenarkiv
• Hval, Halvor Høen; Tripathi, Alok Mani; Forseth, Sissel & Fjellvåg, Helmer (2020). Understanding the details of crystal structure and electronic states in LNMO. Fulltekst i vitenarkiv
• Valberg, Anna Helene & Hval, Halvor Høen (2020). – Kom hit med glød og kunnskapstørst og hjelp oss å forandre verden. [Internet]. uio.no. Fulltekst i vitenarkiv
• Hval, Halvor Høen (2020). Research Outreach: Design and Presentation. Fulltekst i vitenarkiv
• Hval, Halvor Høen (2020). Moderne batteriteknologi - fra Daniell til Nobel, og veien videre. Fulltekst i vitenarkiv
• Hval, Halvor Høen (2020). Om batterier og kjemistudiet. Fulltekst i vitenarkiv
• Hval, Halvor Høen & Kristiansen, Nina (2020). Han skal lage bedre batterier - da må han steke og bake. [Journal]. www.forskning.no. Fulltekst i vitenarkiv
• Hval, Halvor Høen; Ruud, Amund; Forseth, Sissel; Emerich, Hermann; Nilsen, Ola & Fjellvåg, Helmer (2019). Operando investigation of batteries. Fulltekst i vitenarkiv
• Hval, Halvor Høen (2019). Make Batteries Safe Again. Fulltekst i vitenarkiv
• Hval, Halvor Høen; Tripathi, Alok Mani & Fjellvåg, Helmer (2019). High Energy Density Electrodes for Lithium-ion Batteries and Operando Studies. Fulltekst i vitenarkiv
• Hval, Halvor Høen; Tripathi, Alok Mani; Ruud, Amund; Emerich, Hermann; Forseth, Sissel & Nilsen, Ola [Vis alle 7 forfattere av denne artikkelen] (2019). Make Batteries Safe Again. Fulltekst i vitenarkiv
• Hval, Halvor Høen (2019). Make Batteries Safe Again. Fulltekst i vitenarkiv
• Hval, Halvor Høen; Tripathi, Alok Mani; Ruud, Amund; Emerich, Hermann; Forseth, Sissel & Nilsen, Ola [Vis alle 7 forfattere av denne artikkelen] (2019). Make Batteries Safe Again. Fulltekst i vitenarkiv
• Hval, Halvor Høen (2019). Make Batteries Safe Again. Fulltekst i vitenarkiv
• Hval, Halvor Høen (2019). Make Batteries Safe Again. Fulltekst i vitenarkiv
• Hval, Halvor Høen (2019). Slik jobber jeg for å gjøre fremtidens oppladbare superbatterier trygge. www.forskning.no. Fulltekst i vitenarkiv
• Hval, Halvor Høen (2019). Make Batteries Safe Again. Fulltekst i vitenarkiv
• Hval, Halvor Høen; Ruud, Amund; Forseth, Sissel; Emerich, Hermann; Nilsen, Ola & Fjellvåg, Helmer (2018). Operando investigation of batteries. Fulltekst i vitenarkiv
• Hval, Halvor Høen; Ruud, Amund; Forseth, Sissel; Emerich, Hermann; Nilsen, Ola & Fjellvåg, Helmer (2018). Operando investigation of batteries. Fulltekst i vitenarkiv
• Raniseth, Amund Midtgard; Hval, Halvor Høen; Fjellvåg, Helmer & Samarasingha, Pushpaka (2022). Synthesis, structural characterization, electrochemical properties, and thermal stability of Al-substituted LiMn1.5Ni0.5O4. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  One of the interesting lithium-ion battery cathode materials which have been developed over the last 20 years is the lithium manganese nickel oxide (LMNO). However, problems with lifetime remain. Increasing the lifetime of LMNO is crucial to its commercial adoption, and one of the promising techniques to do this is substituting different elements of the structure. In this thesis, the structure, electrochemistry, and thermal stability of LMNO have been investigated with different amounts of aluminum substitution attempted to replace either manganese, nickel, or both elements evenly. The findings suggest that substituting manganese is not easily done, as impurities form. However, by replacing mainly nickel, aluminum is successfully incorporated into the structure at a stoichiometric amount of 0.2. This type of substitution was also found to change the electrochemical voltage plateau of the material, in addition to prolonging its cycle life. The aluminum substituted material also exhibited better thermal stability above 100℃.

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