REVISITING GRAPHITE ANODE AND V₂O₅ CATHODE FOR LITHIUM ION BATTERIES

Lithium-ion batteries (LIBs) are integral to modern energy storage, with graphite serving as the preferred anode material due to its high conductivity, stability, and affordability. However, challenges related to irreversible initial lithium loss, electrolyte compatibility, and lithium-ion transport kinetics limit the performance and efficiency of graphite anodes. This dissertation addresses these critical issues by exploring novel approaches to enhance the functionality of graphite anodes. The first part of the research investigates the loss of lithium during the formation of the solid electrolyte interphase (SEI) on the graphite anode during the initial charge process. To counter this loss, a new method of graphite pre-SEI is introduced. By preforming SEI layers electrochemically on graphite powders, this technique improves the initial Coulombic efficiency of full cells without sacrificing active cathode material, providing a practical solution for offsetting lithium loss. The second part focuses on overcoming the limitations of traditional electrolyte systems. Graphite's tendency to exfoliate in the presence of organic solvents restricts electrolyte choices, particularly those beyond ethylene carbonate (EC)-based solvents. This chapter presents a new electrolyte design featuring nanoscale anion networks formed by concentrated lithium salts. These networks stabilize graphite by preventing solvent co-intercalation, offering new opportunities for LIBs to operate with a broader range of electrolytes while maintaining electrode integrity. The final chapter of this dissertation re-examines the conventional understanding of lithium-ion transport through the SEI. By constructing SEI-rich structures on a niobium oxide (Nb₂O₅) anode, a new mechanism of lithium transport is proposed. Contrary to the widely accepted two-step diffusion model, findings indicate that lithium transport can occur via a one-step pore diffusion process, eliminating the kinetic limitations previously associated with the SEI and enhancing fast-charging capabilities. In the fourth chapter, a surface modification on graphite surface with a electrochemically active layer is demonstrated to improve the surface diffusion of lithium and thus enhance the low-temperature performance of graphite anodes. The next chapter the high energy density V₂O₅ cathode is revisited with multi-nonmetal doping with improved cycling stability. Overall, this dissertation advances the understanding of graphite anodes in lithium-ion batteries by providing innovative solutions to SEI formation, electrolyte design, and lithium-ion transport, paving the way for more efficient and high-performance energy storage systems.