Improvement of electrochemical performance of energy storage devices through 3D structural design of electrodes

Abstract

This thesis aims to enhance the electrochemical performance of energy storage devices through the implementation of a 3D structural design for electrodes. The objective is to overcome limitations and optimize the performance of these devices by modifying the electrode structure. In Part I, we fabricated 3D structured Si electrodes using a pore-forming agent and investigated their physical-electrochemical properties. Lithium-ion capacitors (LICs) are gaining attention from researchers as the demand for an energy storage device that addresses the drawbacks of lithium-ion batteries and supercapacitors is increasing. Silicon (Si) is a desirable anode material for LICs due to its high theoretical capacity and low working potential. However, Si experiences extreme volume changes of up to 300%, which cause a poor cycle life. To mitigate mechanical stress in Si anodes, we fabricated a three-dimensional structured Si electrode using a pore-forming agent and evaluated its physical-electrochemical properties. The pore network of the structured Si electrode effectively buffered the volume change, alleviating crack formation in the electrode and resulting in improved cycle stability. The LIC full cell using the structured Si had a high energy density of 191.4 Wh kg−1 at a power density of 723.7 W kg−1. Our approach is compatible with conventional electrode fabrication systems and provides a cost-effective and practical method for pure Si anodes suitable for use in LICs through a simple pore-structuring process. Part II focuses on the 3D structural design of electrodes using laser structuring techniques. Laser treatment is employed to reduce the internal resistance (Rion) of the electrode and shorten ion migration paths, thereby enhancing power density. Various laser-structuring patterns, such as line patterning and pinhole patterning, are investigated to assess their impact on Rion reduction and active material loss. Electrochemical characterization techniques, including electrochemical impedance spectroscopy (EIS), are used to analyze ion migration behavior and evaluate the performance of laser-structured electrodes. The results highlight the effectiveness of pinhole patterning in reducing Rion while minimizing active material loss. Rate performance tests confirm the improved capacity and rate capability of the laser-structured electrodes compared to pristine electrodes. By combining complex capacitance analysis and 3D structural design of electrodes, this thesis presents a comprehensive approach to improving the electrochemical performance of energy storage devices. These advancements contribute to the development of more efficient and high-performance energy storage systems, addressing the growing demand for reliable and high energy density devices in various applications.