Design and fabrication of high power microbatteries and high specific strength cellular solids from bicontinuous microporous hierarchical materials
An emerging paradigm in engineering design is the development of materials by constructing hierarchical assemblies of simple building blocks into complex architectures that address physics at multiple length scales. These hierarchical materials are increasingly important for the next generation of mechanical, electrical, chemical, and biological technologies. However, fabricating hierarchical materials with nm control over multiple chemistries in a scalable fashion is a challenge yet to be overcome. This dissertation reports the design and fabrication of hierarchical microbattery electrodes that demonstrate unprecedented power density as well as hierarchical cellular solids with controllable modulus and high specific strength. Self-assembly, electrodeposition and microfabrication enable the fabrication of microbatteries with hierarchical electrodes. The three-dimensional bicontinuous interdigitated microelectrode architecture improves power performance by simultaneously reducing ion and electron transport distances through the anode, cathode, and electrolyte. The microbattery power densities are up to 7.4 mW cm-2 μm-1, which equals or exceeds that of the best supercapacitors and which is 2000 times higher than that of other microbatteries. A one dimensional electrochemical model of the microbatteries enables the study of physical processes that limit power performance. Lithium diffusion through the solid cathode most significantly limits the amount of energy extracted at high power density. Experimentally-validated design rules optimize and characterize the battery architecture for high power performance without the need for multiphysics based simulations. Electrochemical deposition techniques improve the microbattery energy density while maintaining high power density by allowing high volume fractions of electrochemically active material to be integrated into the high power architectures. The microbattery energy densities are up to 45.5 µWh cm-2 µm-1, which is greater than previously reported three-dimensional microbatteries and comparable to commercially available lithium-based batteries. This dissertation also demonstrates the fabrication of 3D regular macroporous microcantilevers with Young’s moduli that can be varied from 2.0 to 44.3 GPa. The porosity and deformation mode of the hierarchical material, which depends on the pore structure, determine the Young’s moduli of the microcantilevers. The template technique allows 3D spatial control of the ordered porous structure and the ability to use a broad set of materials, demonstrated with nickel and alumina microcantilevers. Self-assembly and electrodeposition enable the scaling of the hierarchical microcantilever material to areas larger than cm2. The large area nickel cellular solids have specific compressive strengths up to 0.23 MPa / (kg m−3). The specific strength is greater than most high strength steels and titanium alloys and is due to the size strengthening effect of the nanometer scale struts in the porous architecture. The scalable fabrication and detailed characterization of the large area cellular solids provide a route for testing high strength cellular materials in a broader set of engineering applications not available to previous techniques whose material dimensions are limited to tens of micrometers.
High Power, Microbattery, Self-assembly, High strength, Cellular solid, Battery Design, Battery, Hierarchical
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign