Lithium-rich disordered rocksalt cathodes display high capacities arising from redox chemistry on both transition-metal ions (TM-redox) and oxygen ions (O-redox), making them promising candidates for next-generation lithium-ion batteries. However, the atomic-scale mechanisms governing O-redox behaviour in disordered structures are not fully understood. Here we show that, at high states of charge in the disordered rocksalt LiMnOF, transition metal migration is necessary for the formation of molecular O trapped in the bulk. Density functional theory calculations reveal that O is thermodynamically favoured over other oxidised O species, which is confirmed by resonant inelastic X-ray scattering data showing only O forms. When O-redox involves irreversible Mn migration, this mechanism results in a path-dependent voltage hysteresis between charge and discharge, commensurate with the hysteresis observed electrochemically. The implications are that irreversible transition metal migration should be suppressed to reduce the voltage hysteresis that afflicts O-redox disordered rocksalt cathodes.
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http://dx.doi.org/10.1038/s41467-022-32983-w | DOI Listing |
J Mater Chem A Mater
December 2024
Faculty of Applied Sciences, Delft University of Technology 2629 JB Delft The Netherlands
Solid-state batteries currently receive ample attention due to their potential to outperform lithium-ion batteries in terms of energy density when featuring next-generation anodes such as lithium metal or silicon. One key remaining challenge is identifying solid electrolytes that combine high ionic conductivity with stability in contact with the highly reducing potentials of next-generation anodes. Fully reduced electrolytes, based on irreducible anions, offer a promising solution by avoiding electrolyte decomposition altogether.
View Article and Find Full Text PDFAdv Mater
December 2024
Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA.
Rationalizing synthetic pathways is crucial for material design and property optimization, especially for polymorphic and metastable phases. Over-stoichiometric rocksalt (ORX) compounds, characterized by their face-sharing configurations, are a promising group of materials with unique properties; however, their development is significantly hindered by challenges in synthesizability. Here, taking the recently identified Li superionic conductor, over-stoichiometric rocksalt Li-In-Sn-O (o-LISO) material as a prototypical ORX compound, the mechanisms of phase formation are systematically investigated.
View Article and Find Full Text PDFAdv Mater
December 2024
Department of Material Science and Engineering, University of California, Berkeley, CA, 94706, USA.
Mn-rich disordered rocksalt materials with Li-excess (DRX) materials have emerged as a promising class of earth-abundant and energy-dense next-generation cathode materials for lithium-ion batteries. Recently, an electrochemical transformation to a spinel-like "δ" phase has been reported in Mn-rich DRX materials, with improved capacity, rate capability, and cycling stability compared with previous DRX compositions. However, this transformation unfolds slowly over the course of cycling, complicating the development and understanding of these materials.
View Article and Find Full Text PDFJ Am Chem Soc
December 2024
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Despite the potential to increase the energy limit of Li-rich cathodes by using oxygen redox, its practicality has been limited by the accompanying structural changes and voltage hysteresis. While voltage hysteresis is commonly associated with transition metal (TM) migration and oxygen dimerization, the specific contribution of each is unclear. We provide a mechanistic insight into how each of these changes induces hysteresis in a representative Li-rich disordered rocksalt cathode, LiMnTiO.
View Article and Find Full Text PDFACS Nano
December 2024
Institute of Energy: Sustainability, Environment, and Equity, Stony Brook University, Stony Brook, New York 11794, United States.
Significant demand for lithium-ion batteries necessitates alternatives to Co- and Ni-based cathode materials. Cation-disordered materials using earth-abundant elements are being explored as promising candidates. In this paper, we demonstrate a coprecipitation synthetic approach that allows direct preparation of disordered rocksalt LiFeTiO (r-LFTO·C) and spinel structured hybrid LiFeTiO·C (s-LFTO·C) nanoparticles with a conformal conductive carbon coating.
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