MANGANESE-BASED THIN FILM CATHODES FOR ADVANCED LITHIUM ION BATTERY

Lithium ion batteries have been regarded as one of the most promising and intriguing energy storage devices in modern society since 1990s. A lithium ion battery contains three main components, cathode, anode, and electrolyte, and the performance of battery depends on each component and the compatibility between them. Electrolyte acts as a lithium ions conduction medium and two electrodes contribute mainly to the electrochemical performance. Generally, cathode is the limiting factor in terms of capacity and cell potential, which attracts significant research interests in this field.Different from conventional slurry thick film cathodes with additional electrochemically inactive additives, binder-free thin film cathode has become a promising candidate for advanced high-performance lithium ion batteries towards applications such as all-solid-state battery, portable electronics, and microelectronics. However, these electrodes generally require modifications to improve the performance due to intrinsically slow kinetics of cathode materials.

In this thesis work, pulsed laser deposition has been applied to design thin film cathode electrodes with advanced nanostructures and improved electrochemical performance. Both single-phase nanostructure designs and multi-phase nanocomposite designs are explored. In terms of materials, the thesis focuses on manganese based layered oxides because of their high electrochemical performance. In Chapter 3 of the nanocomposite cathode work, well dispersed Au nanoparticles were introduced into highly textured LiNi_0.5Mn_0.3Co_0.2O₂ (NMC532) matrix to act as localized current collectors and decrease the charge transfer resistance. To further develop this design, in Chapter 4, tilted Au pillars were incorporated into Li₂MnO₃ with more effective conductive Au distribution using simple one-step oblique angle pulsed laser deposition. In Chapter 5, the same methodology was also applied to grow 3D Li₂MnO₃ with tilted and isolated columnar morphology, which largely increase the lithium ion intercalation and the resulted rate capability. Finally, in Chapter 6, direct cathode integration of NMC532 was attempted on glass substrates for potential industrial applications.