Abstract
The development of advanced batteries that have a higher energy density for current lithium-ion and beyond lithium-ion battery relies not only on the identification of new chemistries (e.g., a compatible combination of cathode, anode and non-aqueous electrolyte), but also mechanistic understanding of cathode performance during charge-discharge processes. For these reasons we focus on model thin film systems, which provide controllable geometry, orientation and surface roughness. Using pulsed laser deposition, we have grown lithium-based (e.g., LiMn2O4) and magnesium based (MgMn2O4) oxide thin films. Using these model systems, we have explored the electrochemical performance of these materials as new battery cathodes, as well as the intercalation mechanism of cations, namely Mg2+ and Li+, at the electrode/electrolyte interfaces. For example, the cubic phase of MgMn2O4 (MMOC) can only be found in powder form at high temperature (> 950 °C) or high pressure (> 15.6 GPa), but is stabilized as thin films, which exhibited reversible Mg2+ insertion and extraction in non-aqueous electrolyte such as Mg(TFSI)2 in diglyme with associated changes in bulk film structure and Mn-oxidation states. Using in situ X-ray reflectivity we have observed the film structural changes during charge-discharge processes. Our thin film model system studies provide a platform for material design and mechanistic understanding for lithium and beyond lithium-ion batteries. This work was supported by the Joint Center for Energy Storage Research (JCESR) through the Office of Basic Energy Sciences (BES), U.S. Department of Energy (DOE).
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