As demand for electric vehicles and other electronic devices advances in the realm of possibilities, the demand for better-performing batteries with higher energy densities, fast charging capability, longer lifetime, etc… rises. One solution out of the many is to increase the cathode active material(CAM) percentage of the electrode, reducing the inactive material of the electrode. This solution theoretically results in lower parasitic side reactions and increased volumetric energy density. However, with the widely used solvent-based slurry casting processes, it is difficult to achieve high CAM electrodes as electrodes become more prone to cracking. In this study, by utilizing a dry electrode coating process, we fabricate a variety of high NCM percentage electrodes, up to 99.5%, and demonstrate stable full cell cycling of 95%-NCM and 97%-NCM cell with capacity retention of 86.3% and 83% after 100 cycles, respectively. However, 99%-NCM showed lower cycling performance, indicating the existence of an active material to inactive material ratio threshold in the cathode composition. The phenomenon is studied through SEM, 4-point probe test, and EIS data. These results open up possibilities for increasing the active material ratio in electrode fabrication to achieve higher energy density, thus reducing the thickness of the layer and the battery.

Thin film LiPON and LLTO are promising solid electrolyte candidates in the development of next generation batteries. These materials can be deposited via RF magnetron sputtering, which is a technique suitable for thin film mass production. In this work, the deposition conditions for LiPON and LLTO are optimized to improve film quality. The thickness of LiPON films is shown to be tunable with the approximation of deposition rate. LiPON films as thin as 325 nm are produced to exhibit sufficient ionic conductivity and low electronic conductivity. Strong electrochemical performance means LiPON can remain a cohesive film even at very thin scales. With this, LiPON has potential to improve volumetric energy density when implemented into thin film batteries. Bulk LLTO is characterized to relate ionic conductivity to Li amount, and the composition with highest ionic conductivity influences the choice of LLTO sputtering target. LLTO film deposition rate is studied as a function of both RF power and deposition pressure, and RF power is shown to have a much stronger effect on deposition rate. Film delamination issues are addressed by decreasing LLTO film thickness, and adhesion to the Si substrate is maintained during the post annealing process. EDS analysis yields the La/Ti ratios of LLTO films, illustrating changes in LLTO composition due to deposition pressure.

Sodium-ion batteries (NIBs) are a promising solution for grid storage because they are inexpensive, sustainable, and have suitable energy densities. Exploration of energy-dense NIB cathode materials that include abundant and inexpensive elements has led to the investigation of sodium iron manganese oxides. However, these materials suffer from poor capacity retention, and their reaction mechanisms remain that presents an obstacle to their optimization. Herein we optimized a novel co-precipitation method that can be used to synthesize sphere-like meso-structured sodium transition metal (TM) oxide cathode materials. The key parameter for controlling the meso-structure was found to be the synthesis cooling rate and the sphere-like meso-structure improved the capacity and lifetime of the cathodes. Using this same synthesis route, P2-Na2/3FexMn1-xO2 (NFMO) cathodes with three Fe:Mn ratios were prepared. The redox mechanisms dependence on the Fe content were explored with X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations. A Fe:Mn ratio less than 1:2 was found to promote capacity retention. One pathway to improve the energy density of NIB cathodes is to enable oxygen redox activity. Oxygen redox activity was triggered in Na0.8Li0.12Ni0.22Mn0.66O2 (NLNMO) by TM layer ordering, however it was irreversible after the first charge. The mechanism of irreversible oxygen activity in NLNMO was observed with XAS, synchrotron X-ray diffraction (sXRD), pair distribution function (PDF), and DFT. Ni migration was found to be detrimental to the reversibility of oxygen redox activity. In addition to NIB cathodes, the anode performances need to be improved. Specifically, hard carbon (HC), one of the most attractive anode materials for NIB, has a low first cycle coulombic efficiency and poor rate capability. These drawbacks appear to be electrolyte dependent, since ether-based electrolytes can largely improve the HC performance compared to carbonate electrolytes. Using titration gas chromatography (TGC), Raman spectroscopy, cyro-transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), we found that the electrolyte controls the quality of the solid electrolyte interphase (SEI), which in turn, controls the first cycle coulombic efficiency and the rate capability. Overall, this work provides insight on how to improve the design of inexpensive, sustainable, energy-dense NIBs for grid storage.