A bio-inspired approach to increase device-level energy density

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018.Cataloged from PDF version of thesis.Includes bibliographical references (pages 120-153).Battery research has historically focused on improving the properties of the active materials that directly store energy. This research has resulted in active materials with higher specific capacity, increased the voltage of batteries in order to store more energy per electron, and lead to the development of electrolytes and binders compatible with high-performance active materials. However, Lithium-Ion Batteries (LIB) are nearing the limits of energy density achievable using a traditional battery design. Structural batteries are a fundamentally distinct route to optimize device performance, aiming to replace structural materials such as metals, plastics, and composites with multifunctional energy-storing materials. By increasing the device mass fraction that is devoted to energy storage, this strategy could more than double the battery life of electronic devices without requiring improved active materials. In this thesis, I show that rigid, load-bearing electrodes suitable for structural batteries can be fabricated using a novel silicate binder. This binder .can be used to distribute load both within layers and throughout the battery by adhering adjacent battery layers. This innovation turns the entire battery stack into a novel monolithic engineering ceramic referred to as a Structural Ceramic Battery (SCB). Unlike previously published binders, this material does not soften with the introduction of electrolyte, it promotes charge transport within the electrode, and it is compatible with a range of active materials employed in batteries today. This thesis furthermore outlines versatile manufacturing methods making it possible to produce SCBs with a wide variety of shapes and form factors amenable to large-scale production. It is envisioned that this SCB architecture will be used to improve the energy density of both ground-based and flying electric vehicles, and that as improved active material chemistries are discovered they will be dropped in to this architecture in order to promote future increases in vehicle-level energy density.by Alan Ransil.Ph. D

Electronic transport in LNMO, a high-voltage cathode material for Lithium-Ion batteries

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, February 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 86-90).Potential routes by which the energy densities of lithium-ion batteries may be improved abound. However, the introduction of Lithium Nickel Manganese Oxide (LixNi1i/2Mn3/2O4, or LNMO) as a positive electrode material appears to be one of the shortest. LNMO is a high-voltage material, with a voltage of 4.7V, and thus offers a significant energy density boost without straying far outside of the stability window of common carbonate-based electrolytes. Furthermore, it would serve as a drop-in replacement for the positive electrode materials already used. In order to best engineer such devices to take full advantage of the intrinsic transport properties of the material, it is important to develop an understanding of what these transport properties are. For a deep understanding of the material such properties must be related not only to material performance but to the processing conditions and atomic structure of the material. The material may be processed such that it belongs in either the P4 332 or the Fd3m space group, exhibiting either order or disorder respectively of Ni and Mn cations. Such processing has a great effect on the concentrations of electronic charge carriers, and thus an effect on the DC electronic conductivity of the material. This conductivity was thus measured for both processing conditions as a function of the lithiation state, and then related to carrier concentrations via the small polaron model for charge conduction. In such a way, the links betweer processing, structure and properties of this material were elucidated. It is hoped that this work will be built upon in order to engineer the high energy-density batteries of the future.by Alan Patrick Adams Ransil.S.M