Structural engineering of lithium-ion battery electrodes for the production of stable, energy-dense storage




Weeks, Jason Alexander

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Lithium-ion batteries (LIBs) have revolutionized many facets of our everyday life, enabling devices such as cell phones, laptops, and, most recently, electric vehicles to become everyday commodities for consumers. However, as the demands of consumers and the energy requirements of these devices continue to grow, so must the storage capabilities of LIBs. Unfortunately, the chemistry and design space of these devices has remained stagnant over the technology’s lifespan. Several energy-dense density chemistries, such as lithium metal, silicon, and tin, are highly regarded for their lithium storage capabilities,. Yet, the non-advantageous side effects of their lithiation/delithiation (dendrite formation, particle fracturing, excessive SEI growth, etc.) have prevented the practical implementation of these materials. As such, an investigation was conducted to determine how structural engineering can be used to help enable next-generation chemistries and electrode designs for higher energy-density LIBs. Lithium metal touts any anode's highest theoretical capacity and power density; however, the safety risks from dendrite formation, such as electrical short-circuiting and explosions, prevent its utilization. Employing a systematic approach to the characterization of the solid electrode interphase (SEI) displays how electrolyte composition influences the chemical makeup of the SEI and its resulting properties. These results demonstrate how the subsequent modulation of the SEI structure and composition can influence the electrochemical performance and lithium deposition morphology. Similarly, the purposeful design of alloying anode materials, like tin and lead, and their host structures can tune their performance and electrochemistry. Typically, the large mechanical stress from the volumetric expansion during lithiation causes severe capacity fade in these materials; however, implementing a carbonaceous scaffold can drastically increase the stability of these materials. In addition to examining new active materials, the structural engineering of the overall electrode is explored. Metal foil current collectors comprise approximately 15% of the total cell weight in traditional batteries. Implementing a templated slurry casting process using camphene enables the formation of free-standing electrodes with enhanced flexibility and rate capabilities. Compared to classical electrode designs, an increase of 25% in energy density can be achieved by eliminating the gravimetrically dense current collector and increasing lithiation site accessibility.



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